bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymptotic analysis of three‐dimensional pressure interference tests: A point source solution
Authors: Illman Walter A. , Tartakovsky Daniel M.
Published: January 2005

Well test analyses conducted in steady state and transient flow regimes have complementary strengths and drawbacks. While steady state analyses are easy to interpret, they are useful only on a late‐time portion of the data collected during pressure interference tests and do not provide estimates of porosity. Transient type curve and numerical inverse approaches overcome these shortcomings but are harder to analyze, and their reliability can be affected by changing external forcings. We develop a new approach to estimate permeability and porosity from well tests, which is based on an asymptotic analysis of pressure transients during three‐dimensional pressure interference tests. Our approach results in a straight line data fitting, rendering the data interpretation straightforward. It also allows one to use intermediate‐to‐late time pressure data. To illustrate the advantages of the proposed technique, we use it to analyze data from several cross‐hole pneumatic injection tests conducted in unsaturated fractured tuff. We demonstrate that the equivalent permeabilities and porosities obtained from our analysis compare well with their counterparts inferred from more complicated approaches, such as type curve and numerical inverse analyses as well as from a steady state analysis.
The human protein disulphide isomerase family: substrate interactions and functional properties
Authors: Ellgaard Lars , Ruddock Lloyd W.
Published: January 2005

The process of disulphide bond formation in the endoplasmic reticulum of eukaryotic cells was one of the first mechanisms of catalysed protein folding to be discovered. Protein disulphide isomerase (PDI) is now known to catalyse all of the reactions that are involved in native disulphide bond formation, but despite more than 40 years of study, its mechanism of action is still not fully understood. This review discusses recent advances in our understanding of the human PDI family of enzymes and focuses on their functional properties, substrate interactions and some recently identified family members.
Observation of the Products of Ionic Collision Processes and Ion Decomposition in a Linear, Pulsed Time-of-Flight Mass Spectrometer
Authors: Ferguson R. E. , McCulloh K. E. , Rosenstock H. M.
Published: January 2005

A retarding potential technique has been investigated which permits study of secondary processes occurring after ion acceleration in a time-of-flight mass spectrometer. By application of a retarding field near the end of the flight path, peaks due to neutral species and fragment ions formed after acceleration are separated from their parent ion peaks and displayed in the same panoramic mass spectrum. Charge exchange, collision-induced dissociation, and spontaneous (metastable) ion decomposition are easily observed. The identities of initial ions and fragment ions involved in secondary processes can be determined unambiguously without complications of peak overlap.
Vibrational Interactions in Pariser—Parr—Pople Theory. II. Ground- and Excited-State Force Fields
Authors: Donath Wilm E.
Published: January 2005

Expressions are derived for the interaction between ground and excited states to give resonance contributions to the vibrational force field. Two contributions are found: The dominating term reflects largely the change in the bond resonance integral due to bond length variation with some contribution of the electrostatic terms; the other, a relatively small term, is generated by the polarization due to the field generated by a vibrational distortion. Calculations are made for the ground states of a number of aromatics; adequate agreement with experiment is found for benzene and naphthalene.

The possible distortion of molecules and the Born—Oppenheimer approximation are investigated when the resonance interactions become strong. Application is made to the 1B1u and 3B1u states of benzene. Distortion and violation of the Born—Oppenheimer approximation is predicted to occur for the two B1u states of benzene.
Isotope Effects on Vibrational Transition Probabilities. The Schumann—Runge Absorption Bands of 16O2 and 18O2
Authors: Halmann M. , Laulicht I.
Published: January 2005

The integrated absorption intensities of the 4, 0 to 11, 0 bands of the Schumann—Runge system of 16O2 and 18O2 were measured at atmospheric pressure and compared with the Franck—Condon factors for these bands, calculated using a Morse potential and simple anharmonicity corrections. Bands of 16O2 are about 1.5 times more intense than corresponding bands of 18O2, while the calculated Franck—Condon factors of 16O2 are 2 to 4 times as large as those for 18O2.
Heat Capacity of Gases in the Critical Region
Authors: Botch W. , Fixman M.
Published: January 2005

A theory of the heat capacity of a one-component gas in the critical region is based on approximations similar to those previously applied to binary mixtures. The excess constant volume heat capacity per mole is found to be ΔM=(R/16πn0c)(6/l2)32(Tc/T−Tc)12 at the critical number density n0c. l is a short-range correlation length and R is the gas constant. A fit to CO2 data gave reasonable agreement with l=4.5 Å.
Potential Curves for Neutral Atoms and Molecules in the State of Collision
Authors: Jefimenko Oleg
Published: January 2005

Equations for the potential curves of two dissimilar neutral atoms in the state of collision are obtained by means of a ``semiclassical'' atomic model. The curves are tested by comparing the calculated and the observed values of the positions of collision-induced satellite bands in the spectra of Rb–Ar, Rb–Kr, and and Rb–Xe gaseous mixtures.
Satellite Bands in the Spectra of Potassium—Foreign-Gas Mixtures
Authors: Jefimenko Oleg , Williams George M.
Published: January 2005

The collision-induced satellite bands in the spectra of K—foreign-gas mixtures were studied. The foreign gases were helium, neon, argon, krypton, xenon, nitrogen, isomers of pentane (n-pentane, isopentane, neopentane), and isomers of hexane (n-hexane, 3-methylpentane, 2,3-dimethylbutane, neohexane). The experimental results for argon, krypton, and xenon were compared with a recently proposed theory of the bands.
One-Dimensional Lattice Gas
Authors: Runnels L. K.
Published: January 2005

Thermodynamic properties are evaluated for a one-dimensional lattice gas whose interactions satisfy the following conditions: first, arbitrary interactions, even of infinite range, are allowed within an unbroken ``queue'' of particles occupying adjacent sites; and second, the only interactions between queues are between adjacent ones, these interactions depending only on the separation of the neighboring queues. For each type of interaction a certain convergence condition is the only restriction on the form of the interaction. Two ensembles are introduced, a constant free-length ensemble and a generalized ensemble of specified intensive variables. Some examples are worked out, and it is shown generally that the model cannot lead to a first-order phase transition.
Exact Lattice Model of Liquids. One-Dimensional Gas of Hard Lines
Authors: Runnels L. K.
Published: January 2005

The equation of state of a one-dimensional gas of hard lines is calculated exactly using a lattice-gas description. The role of many-body interference effects is studied and found to include an effective repulsion with a logarithmic singularity for compact arrangements of molecules. A sequence of successive approximations is introduced and the rate of convergence to the exact result investigated.
Mercury-Photosensitized Oxidation of Tetrafluoroethylene
Authors: Heicklen Julian , Knight Vester , Greene S. A.
Published: January 2005

The mercury-photosensitized reactions of C2F4 were studied in the absence and the presence of oxygen at room temperature. In the absence of oxygen, the only product was cyclo-C3F6, whereas CF2O and another unidentified product were also formed in the presence of oxygen. The cyclo-C3F6 formation rate was unaffected by oxygen or nitrogen and was proportional to the C2F4 pressure and the square root of the incident intensity. The results are explained. The oxidation apparently does not involve the CF2 radical. Two processes are introduced to explain the oxygenated products. One of these is attack of C2F4 by oxygen atoms produced from the mercury-photosensitized decomposition of oxygen. The other involves the reaction of molecular oxygen with an electronically excited C2F4 molecule. The first oxidation process can be suppressed by the addition of nitrogen, whereas the second cannot. The oxidation mechanism presented is not complete but does explain the major trends.
Susceptibilities of Manganese and Ferrous Formate Dihydrates
Authors: Uryû Norikiyo
Published: January 2005

The magnetic susceptibilities of Mn (HCOO)2·2H2O and Fe (HCOO)2·2H2O are considered by a molecular field approximation. Assuming the four sublattice model and the superexchange interaction between magnetic ions via a formate group, the temperature dependence of the susceptibility can be explained with suitable exchange integral. It is also pointed out that a sharp peak in the susceptibility should originate in the Moriya—Dzialoshinsky interaction.
Spectroscopic Constants and Vibrational Assignment for the B 3Πu + State of Iodine
Authors: Steinfeld J. I. , Zare R. N. , Jones L. , Lesk M. , Klemperer W.
Published: January 2005

Portions of the iodine B 3Π0u+←X 1Σg+ absorption spectrum have been remeasured under high resolution. A new analysis of 719 lines in the 3–6, 4–7, 5–4, 7–5, 11–1, 12–2, 13–2, 25–0, and 29–0 bands, combined with previous measurements by Mecke, Loomis, and Brown, gives the following revised constants: ωe′=125.273 cm−1Te′=15770.59γe′=−4.0×10−7ωexe′=0.7016Be′=0.028969δe′=−3.5×10−8ωeye′=−0.00567re′=3.0276 ÅDe′=3.5×10−9ωeze′=+0.000032αe′=0.0001562βe′=3.9×10−10De′=4391.0Constants for ground state rotational levels were found to be in good agreement with Rank's latest determinations.

Using these new constants for the B state, Franck—Condon factors for this system were computed. The vibrational numbering originally assigned by Mecke and Loomis to the B state was decreased by one unit to bring calculated intensity distribution into complete agreement with all observed fluorescence data, including new photoelectric measurements on a number of bands. No systematic variation of the electronic transition moment could be derived from these data. These revised Franck—Condon factors were also used to recalculate radiative lifetimes from absolute absorption data which are in fair agreement with the phase-shift determination of Brewer, Berg, and Rosenblatt.
Slow-Neutron Inelastic Scattering from Low-Temperature Gaseous Methane, Liquid Methane, and Solid Methane
Authors: Harker Y. D. , Brugger R. M.
Published: January 2005

The partial differential cross sections for inelastic scattering of neutrons from samples of cold gaseous methane (T=125°K), liquid methane (T=99°K), and solid methane (T=83°K) were measured with the materials testing reactor (MTR) phased chopper velocity selector. These results are compared to the theory reported by Griffing for methane gas, which fits the cold-gas data very well over the entire range of the experiment and also fits the liquid and solid data at the large momentum transfers. The results of these comparisons indicate that the rotations are free in all three phases and that, in the liquid and solid phases, there are oscillations of the center of mass of the molecule with dominant transitions having an energy change near 0.017 eV. The range of agreement of the gas theory with the liquid and solid data indicates that the liquid and solid act according to the gas model out to a time of roughly 5×10−13 sec. The similarity of the liquid and solid data over the range of the experiment suggest further that they act similarly out to even longer times.

The zeroth and first moments of energy transfer were calculated and for the gas compare favorably with a molecular theory which treats the rotations classically. For the liquid and solid data, the moments give further indications of the molecular oscillations.
Microwave Spectrum of Methyl Thionylamine
Authors: Rao V. M. , Yardley James T. , Curl R. F.
Published: January 2005

The microwave spectrum of methyl thionylamine (CH3NSO) has been investigated. Only the a-type R-branch transitions have been identified. The components of the dipole moment parallel and perpendicular to the a axis have been found to be μa2=2.74±0.06,μb2=0.14±0.05. The dipole moment is 1.70±0.02 D. The barrier to internal rotation of the CH3 group in CH3NSO has been found to be 335±15 cal/mole. No nitrogen nuclear quadrupole splittings were observed.
Spin Diffusion Measurements: Spin Echoes in the Presence of a Time-Dependent Field Gradient
Authors: Stejskal E. O. , Tanner J. E.
Published: January 2005

A derivation is given of the effect of a time-dependent magnetic field gradient on the spin-echo experiment, particularly in the presence of spin diffusion. There are several reasons for preferring certain kinds of time-dependent magnetic field gradients to the more usual steady gradient. If the gradient is reduced during the rf pulses, H1 need not be particularly large; if the gradient is small at the time of the echo, the echo will be broad and its amplitude easy to measure. Both of these relaxations of restrictions on the measurement of diffusion coefficients by the spin-echo technique serve to extend its range of applicability. Furthermore, a pulsed gradient can be recommended when it is critical to define the precise time period over which diffusion is being measured.

The theoretical expression derived has been verified experimentally for several choices of time dependent magnetic field gradient. An apparatus is described suitable for the production of pulsed gradients with amplitudes as large as 100 G cm−1. The diffusion coefficient of dry glycerol at 26°±1°C has been found to be (2.5±0.2)×10−8 cm2 sec−1, a value smaller than can ordinarily be measured by the steady gradient method.
Triplet Excitons in Crystals of Aromatic Molecules
Authors: Jortner Joshua , Rice Stuart A. , Katz Joseph L. , Choi Sang-Il
Published: January 2005

In the present paper we consider the band structure and the Davydov splitting of the first triplet exciton states in crystalline naphthalene, anthracene, and biphenyl. It is found that: (a) An important contribution to the triplet exciton bandwidth arises from intermolecular exchange interaction. These interactions are calculated in the molecular orbital π-electron approximation. (b) Excitation exchange effects due to spin—orbit coupling are negligible. (c) Nonorthogonality corrections, considered within the framework of the symmetric orthogonalization procedure, have been found to be small. (d) Crystal-field mixing of triplet states arising from π→π* excitations has no effect on the triplet bands. (e) An important contribution to the triplet exciton bandwidth may arise from configuration interaction with charge-transfer states.

The dynamics of triplet excitons in aromatic crystals was studied in the two limiting cases of strong and weak scattering. The band model, with the constant mean-free-path approximation, leads to a mean free path of the order of one to two lattice distances and seems to be inappropriate. Triplet—triplet annihilation leading to delayed blue fluorescence in crystalline anthracene can be adequately described in terms of a random-walk diffusion model when the effects of charge-transfer interactions are included.
Anisotropic Hyperfine Structure in ESR Spectra: Applications to Irradiated Crystals of Malonamide and Glycine
Authors: Rexroad H. N. , Hahn Yu Hak , Temple Wade J.
Published: January 2005

The electron spin resonance spectrum resulting from the anisotropic coupling with one proton is known to consist of two doublets whose splittings and intensities depend on frequency as well as orientation of the magnetic field. The possible appearance of both doublets in the same spectrum can be used to aid the analysis of complicated spectrum. It is used here to establish the existence of more than one radical species in irradiated malonamide and to verify the H(C) coupling constants in NH3+(ĊH)CO2— that were reported earlier by Ghosh and Whiffen in γ-irradiated glycine. A hyperfine coupling tensor having principal values of −29, −59, and −89 Mc/sec was observed in γ-irradiated malonamide and used to identify the radical ĊH(CONH2)2 with the spin density concentrated in a p-orbital of the central carbon atom. The theory of anisotropic magnetic hyperfine interactions is extended to include coupling cases other than a single nucleus with spin ½ and the experimental conditions required for observation of more than the usual 2I+1 hyperfine lines are examined.
Laser Generation of Excitons and Fluorescence in Anthracene Crystals
Authors: Singh S. , Jones W. J. , Siebrand W. , Stoicheff B. P. , Schneider W. G.
Published: January 2005

Experimental and theoretical studies are reported of the short-lived and delayed fluorescence of anthracene single crystals, excited by single- and double-photon absorption. A giant-pulse ruby laser provides the primary source of radiation of 14 400 cm−1 (up to 1027 photons/cm2·sec) and is also used to generate second-harmonic radiation from ADP, as well as stimulated Raman radiation of 12 800 and 17 500 cm−1 from liquid oxygen. The time dependence of the fluorescence intensity is studied as a function of laser intensity, crystal temperature and excitation wavelength. The very intense fast fluorescence with a half-life of 30 nsec at 300°K, characteristic of singlet exciton decay, and the relatively weak delayed fluorescence which involves intermediate triplet states, are separated using sectored disks. It is concluded that the triplet state at 14 750 cm−1 can be populated (i) by direct absorption of laser photons involving an activation energy of 350 cm−1; (ii) via two-photon absorption, presumably leading to a vibrationally excited state of the 1B2u exciton, followed by intersystem crossing; (iii) via one-photon (second-harmonic) excitation from levels≥700 cm−1 into the singlet absorption band, followed by conversion of the singlet exciton into a triplet pair. The latter process is suggested by the observed activation energy of 700 cm−1. In agreement with these interpretations, the delayed fluorescence intensity is found to vary with the second to fourth power of the laser intensity depending on the experimental conditions. Also, light of 17 500 cm−1 leads exclusively to Process (i), light of 12 800 cm−1 exclusively to (ii). Triplet lifetimes from 2–17 msec are obtained, depending on crystal purity, which indicates that unimolecular triplet decay is an extrinsic, radiationless process. A singlet—triplet intersystem crossing rate constant of about 3×10−5 sec−1 is estimated. The triplet—triplet annihilation rate constant is found to be about 5×10−11 cm3 sec−1. This value considered together with the triplet-pair creation process suggests a triplet exchange rate ≳ 1013 sec−1 and a triplet diffusion constant ≳o5×10−4cm2/sec.
Isotopic Determination of the Vibrational Numbering for the B3Π0+u State of Iodine
Authors: Brown Robert L. , James Thomas C.
Published: January 2005

A measurement of the vibrational isotope displacements between 127I2 and 129I2 has confirmed the revised vibrational numbering of the B3Π0+u state proposed by Steinfeld et al. They have observed that the traditional numbering must be decreased by one unit to bring their calculated fluorescence intensity distributions into agreement with experiment.
Vibronic Coupling. III. Adiabatic Potentials and Vibronic Functions
Authors: Gouterman Martin
Published: January 2005

General vibronic equations are given for the coupling of two electronic states in terms of their adiabatic potentials. It is shown that in addition to the adiabatic potentials it is necessary to know U(Q), a unitary transformation that depends on the vibrational coordinates Q. It is suggested that U(Q) be obtained from the ``crude adiabatic'' model. The appropriate U(Q) for the Renner and Jahn—Teller effects are given. A more extensive discussion is given of the pseudo Jahn—Teller effect described in previous papers of this series. Adiabatic potentials are given and it is shown how vibronic energy levels may be related to these potentials.
Infrared and Raman Spectra of α,α,α-Trichlorotoluene, C6H5CCl3
Authors: Stephenson C. V. , Coburn W. C.
Published: January 2005

The Raman spectrum between 3500 and 100 cm−1, including polarization measurements, and the infrared spectrum between 4000 and 265 cm−1 of liquid α,α,α-trichlorotoluene, C6H5CCl3, have been recorded. Wavenumber assignments of the phenyl vibrations have been made on the basis of C2v symmetry, although the molecule is undoubtably of lower symmetry.

The 24-substituent-insensitive ring modes were assigned without much difficulty. The nine substituent modes and the six substituent-sensitive ring modes were assigned with less certainty, but the Raman polarization data helped in the assignment of some of these. The phenyl-substituent torsional mode was assigned to the strong, broad Raman line observed at 118 cm−1. The six phenyl vibrations whose wavenumbers are sensitive to the nature of the substituent were assigned, in our previous notation [C. V. Stephenson, W. C. Coburn, Jr., and W. S. Wilcox, Spectrochim. Acta 17, 933 (1961)], as follows: ν20′(δCC)b2, 176 cm−1;ν14′(βCX)b1, 246 cm−1;ν18′(αCCC)a1, 308 cm−1;ν19′(γCX)b2, 507 cm−1;ν2(νCX)a1  629 cm−1;and ν2(νCX)a1; 1185 cm−1.
Raman Spectra of Polycrystalline Methylene Halides
Authors: Ito Mitsuo
Published: January 2005

The Raman spectra of CH2Cl2, CH2Br2, and CH2I2 have been observed at 77° and 195°K. Band splitting due to the crystal field has been found for the Raman bands ν3, ν4, and ν9 of CH2Cl2 and for the band ν1 of CH2Br2. No apparent splitting has been observed for the Raman bands of CH2I2. The band splittings and frequency shifts of the intramolecular vibrations are discussed.

The Raman bands due to the lattice vibrations have been obtained and tentative assignments are presented for some of the bands. Much temperature effect has been found on the Raman frequencies of the lattice vibrations.
Molecular Orbital Analysis of Iron-Group Cyanides
Authors: Shulman R. G. , Sugano S.
Published: January 2005

In the iron-group cyanides the low-lying antibonding orbitals of the cyanide ligands do not contain electrons. These π* orbitals play an important role in the covalency of the complexes. A molecular orbital analysis of their role is presented in order to correlate the orbital reduction factors derived from the ESR experiments of Baker, Bleaney, and Bowers with the isomer shifts of the Mössbauer experiments. By fitting the wavefunctions to the ESR experiment it is shown that the Fe2+ complex donates about one more electron to the π* orbitals than does the Fe3+. This shows that the effective charges of Fe2+ and Fe3+ are approximately the same and explains their similar isomer shifts.
Binding of Mn2+ to Nucleic Acids
Authors: Eisinger J. , Fawaz-Estrup F. , Shulman R. G.
Published: January 2005

Measurements of the nuclear magnetic resonance relaxation times T1 and T2 of the water protons in aqueous solutions of nucleic acids and magnetic metal ions allow one to determine details about the metal-ion binding. When Mn2+ is bound, the rotation of its hydration sphere becomes slower, so that its effectiveness in reducing the proton T1 from its value in pure water is enhanced. This relaxation enhancement has been measured for Mn2+ bound to DNA, RNA, synthetic polynucleotides, and E. coli ribosomes. Compared to water as unity, the enhancement factors range from 3.7 for polyuridylic acid to 16.7 for polyadenylic acid. The equilibrium constants for binding, and the concentration of binding sites have been calculated from the dependence of enhancement upon Mn2+ concentration.
Zero-Field Splittings and Spin Densities in Ground-State Triplet Aromatic Nitrenes
Authors: Coope J. A. R. , Farmer J. B. , Gardner C. L. , McDowell C. A.
Published: January 2005

This paper outlines a simple semiempirical theory of the zero-field splitting parameters of aromatic nitrenes. The theory is based on a Hückel LCAO description of the aromatic system, and takes advantage of the vanishing of odd orbital mutual atom polarizabilities in odd alternant molecules. The observed parameter for the parent imine radical is used as an empirical one-center integral. Calculated parameters agree rather well with electron spin resonance results. The relation between the zero-field parameters and general π-electron spin densities is also outlined.
Dependence of the Probabilities of Vibrational De-Excitation on Interaction Potentials
Authors: Shin Hyung Kyu
Published: January 2005

Using the WKB semiclassical approximation, the dependence of the probability of vibrational de-excittion on the assumed form of the interaction potential is discussed. The asymptotic results show that the Morse and Lennard-Jones potentials have, respectively, two and three correction terms in the exponential part. The magnitudes of the correction terms are important compared to the leading term. The exact form of the leading term is also dependent upon the interaction potential.
Electron Spin Resonance of Irradiated Quartz: Atomic Hydrogen
Authors: Weeks R. A. , Abraham M.
Published: January 2005

An electron spin resonance spectrum observed in irradiated synthetic quartz crystals is attributed to atomic hydrogen in interstitial sites. The quartz specimens were irradiated with 1.7 MeV electrons at ∼300°K (1018 electrons cm−2) and then with 60Co γ-rays (∼107 R) at ∼80°K and measurements were made without warming. The hydrogen spectra had a hyperfine constant A = 521.3 Oe (1453.1 Mc/sec) when the applied field was along the crystal threefold axis. An anisotropy of the hyperfine interaction of the order of 0.75 Oe was detected. The g value was 2.0021±0.0005 and evidence for a small variation in this value with rotation was inferred. There are three sites for the atomic hydrogen in the unit cell which are related by the three fold symmetry operator of the crystal and which are otherwise equivalent. Additional hyperfine interactions with 29Si nuclei were also observed enabling a tentative model of the sites to be proposed. The width of the line was 0.1 Oe and was attributed mainly to field inhomogeneity. Another spectrum was observed with a slightly smaller hyperfine interaction and was also attributed to atomic hydrogen in a different interstitial site. Detailed measurements were not made due to the low intensity of the spectrum.
Phase Separation by Spinodal Decomposition in Isotropic Systems
Authors: Cahn John W.
Published: January 2005

The theory of phase separation from a single phase fluid by a spinodal mechanism is given. The predicted structure may be described in terms of a superpositioning of sinusoidal composition modulations of a fixed wavelength, but random in amplitude, orientation, and phase. Sections through a calculated structure are shown. These show that the structure has many of the geometrical features found in phase separable glasses, in particular the high degree of connectivity among particles of each phase.
Magnetic Moment and Susceptibility of MnCl2 as a Function of Field along the b Magnetic Axis to 95 kG from 1.3° to 4.2°K
Authors: Giauque W. F. , Fisher R. A. , Hornung E. W. , Butera R. A. , Brodale G. E.
Published: January 2005

Values of magnetic moment, isothermal differential susceptibility, magnetic work and free energy change of single-crystal MnCl2 have been obtained by means of a digital voltmeter integrating the dc potential on a sensing coil surrounding a spherical sample. This substance becomes antiferromagnetic near 2°K. The sample was moved vertically along the measuring coil axis which coincided with the field direction in an accurately stabilized field in a long solenoid. The observations cover the range from 1.3° to 4.2°K and fields to 95 kG. The measurements show no signs of irreversibility over the above region. The sample was high purity anhydrous MnCl2 with its b magnetic axis (a crystallographic axis) parallel to the field. The saturation value of MnCl2 was found to be 27 988 G·cm3/mole corresponding to a g=2.004 for a 6S52 state. Problems connected with the accurate use of digital integrators for such measurements are discussed and illustrated by means of various experiments. Magnetic effects due to air, should leaks occur into a refrigerant under vacuum within a solenoid, are discussed and a method of removing solid air from the region near the magnetic sample during magnetic measurements is suggested.
Cole—Cole Diagram and the Distribution of Relaxation Times
Authors: Fang P. H.
Published: January 2005

The completeness of the Cole—Cole diagram in the analysis of dielectric relaxation is proved by showing explicitly that a semicircle in the Cole—Cole diagram corresponds uniquely to a Debye relaxation function. A method is established to distinguish a continuous distribution of relaxation times from a single relaxation time.
On the Effect of Adsorbed Particles on the Accommodation Coefficients
Authors: Shin H.
Published: January 2005

By use of a classical model, the effect of adsorbed particles on the accommodation coefficients at a gas—solid interface is studied. The interaction between the adsorbed and incident particles is assumed to be impulsive. The results show an important contribution of this effect on the over-all value of the accommodation coefficients even at the surface coverage as low as 1%.
Second and Fourth Moments of Chain Molecules
Authors: Flory P. J. , Jernigan R. L.
Published: January 2005

Exact methods are developed for calculating second and fourth moments 〈M2〉 and 〈M4〉 of chain molecules, where M= ∑ i=1nmiand mi is a vector associated with Bond i but not necessarily colinear with it. The rotational isomeric-state approximation is adopted to represent the effects of hindrance potentials affecting bond rotations. No other approximations are invoked in deriving the statistical-mechanical averages denoted by 〈 〉. Account is taken of neighbor correlations, and the treatment is applicable alike to finite and infinite chains. Illustrative calculations of 〈r2〉/nl2 and of 〈r4〉/n2l4, where r is the end-to-end length of the chain, l the bond length, and n the number of bonds, are presented for normal alkane homologs H–(CH2)n–H, throughout the range of n from 1 < n < ∞. The methods are applicable also to chains having any variety of bonds in linear succession.
Ultrasonic Attenuation Measurements in Poly-l-Glutamic Acid Solutions
Authors: Burke J. J. , Hammes Gordon G. , Lewis Thomas B.
Published: January 2005

Ultrasonic attenuation measurements of poly-l-glutamic acid in 0.2M NaCl(aqueous)—dioxane (2:1) have been carried out over a frequency range from 6 to 175 Mc/sec using a pulse-echo method. Attenuation in excess of the pure solvent was found over the entire pH range investigated (5.4–9.0). A distribution of relaxation times is observed at all pH values. This distribution approaches a single relaxation time as the pH is raised. The amplitude parameter characterizing the attenuation and the average relaxation time does not vary markedly with pH. The amplitude parameter is approximately proportional to the polymer concentration, in contrast to the average relaxation time which is not strongly dependent on the polymer concentration. The process primarily responsible for the observed chemical relaxation is probably the interaction between solvent and polymer. The minimal volume change associated with the observed process has been calculated and is approximately ±3 cc/mole of monomer. Although the ultrasonic attenuation clearly depends on whether the polymer molecule is in the form of a helix or random coil, the transition from helix to coil is not primarily responsible for the observed excess absorption. By combining these results with other data, bounds for the average relaxation time characteristic of the helix—coil transition can be estimated as 5×10−8<τ̄<10−5 sec.
Hydrogen Molecular Ion: Solutions of the Schrödinger Equation Expressed as Integral Equations
Authors: McKinney Paul Caylor
Published: January 2005

The ordinary differential equations which arise from the separation of the Schrödinger equation for the hydrogen molecular ion in prolate spheroidal coordinates are investigated to find exact solutions in the form of integrals. Such solutions are found to be homogeneous Fredholm integral equations of the second kind. Appropriate kernels for the integral equations are explicitly determined and the elementary properties of the wave-equation solutions are discussed.
Electron Spin Resonances in Gamma-Ray Irradiated Sodium Chlorate. I
Authors: Gamble F. T.
Published: January 2005

Single crystals of NaClO3 were subjected to gamma-ray irradiation at room temperature. Analysis of the resulting electron spin resonance spectrum indicates the production of three paramagnetic centers, initially, each with an effective spin of ½. The measured parameters of a center having resolved hyperfine structure and identified as ClO3 were g∥ = 2.0085±0.0010, g⊥ = 2.0090±0.0010, A = 14.8±0.1 G, and B = 21.2±0.1 G. No hyperfine interaction was detected for the remaining two centers having g∥ = 2.007±0.001 and g⊥ = 2.020±0.001, and g≃2.008, respectively. The centers are reasonably stable at room temperature for several months.
On the Use of Overhauser Effects to Study Nuclear Magnetic Relaxation by Spin—Rotational Interactions
Authors: Hubbard Paul S.
Published: January 2005

It is shown that the contributions of spin—rotational and dipole—dipole interactions to the nuclear magnetic relaxation of liquid samples containing two different kinds of spin-½ nuclei can be determined from the results of measurements made at a single temperature of the transient and steady-state Overhauser effects and the relaxation rates of each kind of nucleus.
Correlated Orbitals for Excited States of He and H—
Authors: Pritchard H. O. , Wallis Anthony
Published: January 2005

Product wavefunctions including exponential correlation terms have been investigated for the excited states of the helium atom and H—.

Transformations are given for the calculation of sp, sd, sf···state integrals.
Solubility and Structure of Mercuric Halides
Authors: Eliezer I.
Published: January 2005

The solubilities of mercuric halides in series of paraffinic and aromatic solvents and in dioxane, as well as in mixtures of these solvents, have been measured. The results are discussed in terms of solvent—solute interactions and their influence on the configuration of the mercuric halides in solution. The solubility trends in pure aromatic solvents show similarities to the behavior of the iodine—aromatic solvent and silver salt—aromatic solvent systems. It is suggested that donor—acceptor complexes are formed between the mercuric halides and some of the solvents examined. The solubilities in mixed solvents indicate a 2:1 solvent:solute ratio which suggests distorted tetrahedral mercuric halide—solvent complexes. In some cases mixed solvates seem to be formed.
Electrical Properties of Single Crystals of Pyrene—Tetracyanoethylene Charge-Transfer Complex
Authors: Tobin Marvin C. , Spitzer Donald P.
Published: January 2005

Transient photocurrents injected with a microsecond light flash and steady-state currents with an illuminated electrode are reported for large single crystals of pyrene—TCNE. Charge-carrier mobilities are calculated at a series of temperatures from the transient measurements. Hole mobilities at room temperature were as high as 30 cm2/V·sec. Electron mobilities were about three orders of magnitude lower. The hole mobility appeared to have a large activation energy—about 0.5 eV.
Unrestricted Hartree—Fock Calculations. II. Spin Properties of Pi-Electron Radicals
Authors: Snyder Lawrence C. , Amos Terry
Published: January 2005

Unrestricted Hartree—Fock wavefunctions have been computed for a large number of conjugated-hydrocarbon pi-electron radicals. Pi-electron spin-density and charge-density functions have been computed with and without annihilation of the major contaminating spin multiplet in the wavefunction.

Three different empirical relations have been used to relate our results to proton isotropic hyperfine splittings measured in ESR experiments. These are the simple McConnell expression; the Colpa and Bolton relation which includes a term depending on the excess charge density at the carbon atom; and that due to Giacometti, Nordia, and Pavan which introduces a contribution from the spin densities in the bonds between the carbon and its nearest neighbors. When the Pariser—Parr method with semiempirical electron-repulsion integrals is employed in the unrestricted Hartree—Fock calculation, then the experimental splittings are almost always bounded by those computed with spin densities before and after the annihilation of the major contaminating spin state, but spin densities after annihilation are closer to the experimental values derived with the empirical relations. This was found to be true for all the three relations used, but the simplest one gave slightly less satisfactory results.

The general problem of the interpretation of spin densities obtained from an unrestricted Hartree—Fock wavefunction which is not an eigenstate of spin is discussed. It is found, however, that unrestricted computations with semiempirical integrals give small splittings of the underlying ``closed''shell orbitals, so that a single annihilation is a good approximation to projection and the spin densities after annihilation should be satisfactory from a theoretical point of view.
Electron Paramagnetic Resonance Spectra of Zinc-Doped Copper Acetate Monohydrate
Authors: Kokoszka Gerald F. , Allen Harry C. , Gordon Gilbert
Published: January 2005

The electron paramagnetic resonance of the copper—zinc pairs in zinc-doped copper acetate monohydrate has been observed at 77°K by using an X-band EPR spectrometer. Single crystals containing less than 1% zinc ions were grown from a slightly acidic aqueous solution containing about 75% copper acetate and 25% zinc acetate.

The experimental results could be fit to the spin Hamiltonian: H=gzβHzSz+gxβHxSx+gyβHySy+AzSzIz+AxSxIx+AySyIy.The values Az=0.0147±0.006 cm−1, Ax<0.0018 cm−1, and Ay<0.0023 cm−1 were measured for the doublet-state cupric ions. The g values were found to be: gz=2.344±0.005, gx=2.052±0.007, and gy=2.082±0.007.

These results are consistent with the model proposed by Slichter, in which he has shown that the components of the hyperfine tensor should be twice as large for a doublet species as compared to the corresponding triplet species when the exchange integral J is much larger than the components of the hyperfine tensor.

Since the microsymmetry at the cupric ion site is no higher than C2v, the EPR results were interpreted by using the theory of Bleaney, Bowers, and Pryce for lower than axial symmetry. The optical data have been interpreted on the basis of weakly interacting cupric ions. A consistent explanation for the magnetic resonance data and optical data is discussed.
Dipole Moments of Terminal Diacetylenes in the Gaseous Phase
Authors: Hayman H. J. G. , Weiss Shmuel
Published: January 2005

The dipole moments of four terminal diacetylenes and three terminal monoacetylenes were measured in the gaseous phase at 35°C using a high-precision heterodyne beat apparatus. The results obtained were interpreted in terms of primary and induced bond moments on the assumption that the above compounds exist as equilibrium mixtures of rotational isomers corresponding to trans and gauche conformations of the various C–C bonds. The composition of these equilibrium mixtures of rotational isomers was assumed to depend on a single parameter expressing the relative stability of gauche and trans conformations. The value of this parameter found from our results agreed satisfactorily with the results obtained by Bartell and Kohl from electron-diffraction measurements on n-paraffins.
Efficiency of Eu3+ Fluorescence in Oxygen-Dominated Host Lattices
Authors: Borchardt Hans J.
Published: January 2005

The efficiency of Eu3+ fluorescence in a variety of rare-earth oxygen-dominated host materials was measured under excitation by 2537 Å uv at 25°C. It was found to be of the same order as that of the commercial phosphor, magnesium arsenate:Mn in all such hosts. To account for the high efficiency and particularly for the insensitiveness of efficiency to the nature of the host lattice, it is proposed that europium—oxygen states are excited directly and that the corresponding absorbtion coefficient is of a magnitude to make this the dominant absorption process.
Enthalpies of Mixing in Silver Bromide—Alkali Bromide and Thallium Chloride—Alkali Chloride Liquid Mixtures
Authors: Hersh L. S. , Navrotsky A. , Kleppa O. J.
Published: January 2005

The enthalpies of mixing in silver bromide—alkali bromide and thallium chloride—alkali chloride liquid mixtures have been determined by high-temperature reaction calorimetry.

The following semiempirical relations represent the molar enthalpies of mixing to a good approximation: AgBr–AlkBr:  HM=N1N2(U0+++52δ12−340δ122) kcal/mole,TlCl–AlkCl:  HM=N1N2(U0+++21δ12−340δ122) kcal/mole.In these expressions N1 and N2 are the mole fractions of the two components, while δ12 = (d1 — d2)/d1d2, when d1 and d2 are the sums of the ionic radii in the two component salts. The positive term U0+ + differs from system to system. It represents a theoretical estimate of the contribution to the mixing enthalpy which arises from the dispersion interaction between next-nearest-neighbor cations, calculated by an adaptation of the method of Mayer.

These expressions are similar to the ones previously determined for the silver chloride—alkali chloride and silver nitrate—alkali nitrate systems, except for the coefficient of the term linear in δ12. This term is absent in the corresponding expression for the binary alkali halides and nitrates. For the considered silver systems, it increases in the sequence NO3—<Cl—<Br—. The term is attributed to the partly covalent bonding between cations and anions in the silver and thallium salts.
Microwave Spectrum, Isomeric Form, and Dipole Moment of 1,1-Difluorobutadiene
Authors: Beaudet Robert A.
Published: January 2005

The microwave spectrum of 1,1-difluorobutadiene has been studied. The small inertial defect indicates that the molecule is planar. From the allowed transition selection rules and the magnitudes of the moments of inertia, the molecule is shown to exist predominantly as the trans isomer. Attempts to find the spectrum of the cis form were unsuccessful.
Correlations between Photoinduced EPR and Photoconductivity in TCNE—THF Solution Charge-Transfer Complex
Authors: Ilten David F. , Calvin Melvin
Published: January 2005

Reversible photoinduced electron paramagnetic resonance (EPR) signals and photoconductivity were observed when a solution of tetracyanoethylene (TCNE) in tetrahydrofuran (THF) was irradiated in the charge-transfer band of the complex formed between these two compounds. The eleven-line hyperfine structure of the EPR spectrum which was obtained demonstrated the presence of TCNE negative-ion radical. The concentration of this radical was found to be directly proportional to the square root of the light intensity. Second-order decay kinetics were followed when the light was shut off. Both the EPR signal and the photoconductivity rose initially as the square of the time. The latter portions of the growth curves could be fit to the latter portions of a hyperbolic tangential growth curve. From these data a reaction mechanism was proposed. The rate law dn/dt+kn2−αL(1−e−βt)=0, where n is the concentration of radicals, t is the time, k, α, and β are rate constants, and L is the light intensity, described both the photoinduced EPR and the photoconductivity within the limits of experimental accuracy.
Collective-Coordinate Treatment of Electrolytes
Authors: Eisenthal K. B. , McMillan W. G.
Published: January 2005

The configuration integral for an electrolyte in a continuous dielectric medium is calculated using the method of collective coordinates. The pair potential energy is taken to be Coulombic (with fixed dielectric constant) for all interionic distances outside some separation a and zero inside. This form permits handling the potential energy completely within the collective-coordinate framework, but has the disadvantage of limiting the concentration to which the treatment is applicable.

For low concentrations, the configurational partition function can be approximated to yield an analytic expression for the activity coefficient. For higher concentrations a numerical integration is used to calculate the mean molal activity coefficients for univalent salts in water at 25°C. The theoretical values obtained from the numerical integrations are within experimental error of the observed values up to molalities of 0.30 to 1.0, depending on the salt considered. As the concentration of the electrolyte goes to zero, the activity coefficient correctly tends to the Debye—Hückel limiting law.
Ionization of Atoms by Collision with Excited Atoms
Authors: Katsuura Kanji
Published: January 2005

Ionization of atoms by collisional transfer of electronic excitation energy, A*+B→A+B++e, is considered theoretically. A formula for the cross section is derived for the case where the transition A→A* is optically allowed and the excitation energy of A* is larger than the ionization potential of B, and is applied to several examples where A* is He (21P).
Electronic Properties of the Tungsten Bronzes
Authors: Fuchs Ronald
Published: January 2005

The magnetic susceptibility and specific heat of the metallic sodium tungsten bronzes NaxWO3 are explained by a model in which the Fermi energy does not depend on the sodium concentration x. The disappearance of metallic conductivity at small x is associated with finite cluster sizes of sodium atoms. Expressions are derived for the dependence of the conductivity on x in the metallic region.
Mass-Spectrometric Study of Photoionization. III. Methane and Methane-d4
Authors: Dibeler Vernon H. , Krauss Morris , Reese Robert M. , Harllee Frederic N.
Published: January 2005

Photoionization-efficiency curves for the molecule and fragment ions of CH4 and CD4 are obtained in the wavelength region 1000 to 600 Å. The electronic structure of the molecule ion is related qualitatively to the shape of the parent-ionization-efficiency curve and the implications of the complicated vibronic behavior of the CH4+ ion are discussed. A qualitative explanation is given for the observed isotope effect on the parent-ionization-efficiency curve and on the fragment-ion threshold energies. New upper bounds for the ionization energies I(CH4) = 12.71 eV and I(CD4) = 12.87 eV are obtained. Other thermochemical values deduced from the study are: D(CH3–H) = 4.41 eV, D(CD3−D) = 4.55 eV, D(CH2–H) = 4.87 eV, and ΔHf (CH2) = 4.07 eV. Zero-point differences for methyl and methylene ions and neutrals are also estimated.
Nuclear Magnetic Resonance in RbMnF3
Authors: Payne Richard E. , Forman Richard A. , Kahn Arnold H.
Published: January 2005

A nuclear magnetic resonance study of 85Rb, 87Rb, and 19F in paramagnetic RbMnF3 is reported. The measured shifts of the rubidium nuclear resonances are the first reported for the case of an alkali nucleus in the paramagnetic XMF3 perovskite compounds (X = Na, K, Rb, Cs; M = Mn, Ni, Co). The shift for rubidium is in the opposite direction from that expected from a 5s contact hyperfine interaction. The isotropic hyperfine interaction of the fluorine indicates the presence of 0.51% unpaired 2s spins in the F— orbitals from each Mn+ + neighbor; this result is in good agreement with previous work for the F— resonances in these paramagnetic materials. The anisotropic shift of the F— resonance was examined in a powder sample and a 2p hyperfine coupling coefficient obtained.
Hypervirial Theorems and the Hellmann—Feynman Theorem in Different Coordinate Systems
Authors: Epstein Saul T.
Published: January 2005

It is shown that the difference between the Hellmann—Feynman theorems in two different coordinate systems is, in general, a hypervirial theorem.