bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Gaussian-Lobe Representation of Atomic Orbitals
Authors: Harrison James F. 
Published: January 2005

The reliability of angularly dependent properties calculated from wavefunctions constructed over a nonnuclear-centered Gaussian basis has been explored by examining the spherical harmonic expansion of the Gaussian-lobe function representation of a pz function. It is found that the component of pz in the Y10 subspace is similar to a double-zeta function while the component in the Y30 subspace is several orders of magnitude less than the Y10 component.
Expectation values for several angularly dependent operators are evaluated over the Gaussian-lobe function representation of a pz orbital and compared with the expectation value calculated over the corresponding double-zeta function. The small angular asymmetry in the Gaussian-lobe function representation of the atomic pz orbitals is reflected in the similarity between the two expectation values.
Electrical Properties and Electronic Configuration of the Monocarbide, Monophosphide, and Monosulfide of Plutonium
Authors: Kruger O. L. , Moser J. B. 
Published: January 2005

The electrical properties of PuC, PuP, and PuS were measured over the temperature range of 300° to 1000°K. The monocarbide and monophosphide had resistivities of 257 and 752 μΩ·cm, respectively, at room temperature; these values did not change appreciably with temperature. Plutonium monocarbide is a p-type conductor with a low absolute thermoelectric power which is only slightly temperature dependent. The monophosphide is also a p-type conductor at room temperature, but it changes to an n-type conductor above 740°K. The quasimetallic conduction of PuC and PuP is essentially proportional to the mobility as indicated by thermoelectric power measurements.
Plutonium monosulfide was found to be an intrinsic semiconductor from 425° to 700°K with an activation energy for conduction of 0.240 eV. Calculations show that above 700°K PuS becomes degenerate as the carrier concentration exceeds 1019 cm−3 and a gradual transition to metallic conductivity is indicated. A peak in the absolute thermoelectric power of 115 μV°K−1 was observed for this compound which is an n-type conductor over the temperature range studied.
In these plutonium compounds and similar actinide compounds conduction appears to be governed by a systematic change of carrier concentration in the s+d valence band and scattering caused by s+d, f transitions. A split in the f states is proposed as the mechanism responsible for the semiconductor properties of PuS.
A comparison was made of the compound unit cell volumes and metal radii for the rare-earth and actinide mononitrides, monophosphides, and monosulfides. The data indicate effective valences of four electrons per atom for the actinide mononitrides and between three and four electrons per atom for the actinide monophosphides and monosulfides.
These plutonium compounds do not have much promise as thermoelectric materials because their figures of merit are all too low for acceptable power generation.
Barrier Studies in the Halopropenes. II. Microwave Spectra, Molecular Structure, Dipole Moment, and the Barrier to Internal Rotation of the Methyl Group in 1,1-Difluoropropene
Authors: Weiss V. W. , Beak P. , Flygare W. H. 
Published: January 2005

1,1-Difluoropropene has been synthesized and characterized by study of the 19F and H nuclear magnetic resonance spectra, infrared spectra, and mass spectra.
The microwave spectra in the ground and first excited torsional states are assigned giving the following rotational constants for the A-type torsional levels: Ground state, A = 10 154.30, B = 3742.19, and C = 2779.33; first excited torsional state, A = 10 098.00, B = 3741.80, and C = 2781.80 (all in megacycles per second). The barrier to internal rotation of the methyl group was determined from the rotational spectra to be V3 = 1252±20 cal/mole. The molecular-dipole components along the principal inertial axes are determined by the Stark effect to be ua = 0.836±0.005 and ub = 0.309±0.005 D with the total dipole being u = 0.889±0.007 D.
The barrier to the internal rotation of the methyl group is discussed in terms of the interaction of the methyl group and the cis substituent. It is concluded from the difference in the barriers between cis-fluoropropene and 1,1-difluoropropene that the barrier is insensitive to small changes in the distance between the cis-fluorine atom and the methyl group.
Deuteron Magnetic Resonance and Proton Relaxation Times in Ferroelectric Ammonium Sulfate
Authors: O'Reilly Donald E. , Tsang Tung 
Published: January 2005

The deuteron nuclear magnetic resonance of single crystals of (ND4)2SO4 has been studied from 77° to 300°K and particularly in the region of the first-order ferroelectric phase transition at 223°K. At high temperatures four closely spaced pairs of lines (10-G max separation) are observed, which shift abruptly as the crystal is cooled through the transition temperature (Tc). These lines are assigned to the two inequivalent ND4+ ions (I and II) in a unit cell, which are slightly distorted from the tetrahedral configuration and rapidly reorienting so as to average the quadrupolar splitting to a small value. At 130°K only two pairs of closely spaced lines are observed due to ND4+ (II); at 77°K eight pairs of widely spaced (400-G max separation) lines are observed corresponding to ND4+ (I). In the transition to the ferroelectric phase the principal coordinate system of the electric-field gradient (EFG) tensor rotates by about 30° for each ion with little change in the coupling constants or asymmetry parameters. The spontaneous polarization produced by the distorted ions has been calculated from the observed EFG tensors and is in reasonable agreement with the experimental value.
Proton spin—lattice relaxation times (T1) and proton relaxation times along the rf field (T1ρ) have been measured for polycrystalline (NH4)2SO4. T1 versus temperature (T) has two minima, and may be interpreted as due to the two inequivalent NH4+ tetrahedra reorienting at different frequencies and coupled to each other via dipole—dipole interaction. Correlation times τc at various temperatures have been obtained for the two inequivalent NH4 ions from the T1 and T1ρ measurements; above Tc and below 170°K, logτc is a linear function of T−1, with normal values of pre-exponential factors. The activation energies change only slightly at the transition, in agreement with recent neutron inelastic scattering data. τc is, however, anomalously short immediately below Tc due to the volume contraction of the crystal. Correlation times have also been estimated from deuteron resonance linewidths and proton second moments. The results are consistent with those derived from the proton T1 and T1ρ data.
An order—disorder mechanism is proposed for the phase transition in which NH4+ tetrahedra are disordered with respect to the crystal ab plane. A first-order transition is described by the molecular field approximation for a sufficiently strong dependence of the interaction parameter on the spontaneous polarization.
Geometry of the Lowest Triplet State of Benzene
Authors: Nieman G. C. , Tinti D. S. 
Published: January 2005

The phosphorescence, fluorescence, and absorption spectra of seven isotopic benzenes in a C6D6 host crystal were obtained at 4.2°K. The isotopes having less than D3h symmetry show splittings in their phosphorescence and singlet absorption spectra. Expected splittings in the fluorescence spectrum have not yet been observed because of the greater difficulty in obtaining the required high-resolution fluorescence spectra. The splittings are interpreted in terms of a distortion, which may arise either from extrinsic or intrinsic perturbations, in the 1B1u and 3B1u states of crystalline benzene. This distortion causes conformers of isotopic benzenes with less than trigonal symmetry to have different zero-point energies and leads to the observed line multiplicity. The vibronic structure of the phosphorescence and fluorescence emissions implies that the magnitude of the distortion is small.
Benzene molecules in the low-symmetry crystalline field are not expected to retain a hexagonal shape. However, the splittings in the fluorescence are only about ⅛ as large as those in the phosphorescence, implying that the distortion in the 3B1u state is larger than that in the 1B2u state. There is therefore some cause to believe that the distortion in the 3B1u state is partly intrinsic and thus has the significance attached to it by theorists. Our experiments, however, cannot actually distinguish between intrinsic and extrinsic distortions, but certainly give the impression that the distortion of the 3B1u state of benzene in the crystal is not very substantial and is either wholly or partly caused by the effect of the crystal field.
The relative intensities of the components of the multiplet structure in the phosphorescence are strongly concentration dependent because of trap-to-trap excitation migration in the crystal. At low guest concentrations, where little migration can occur, the intensity ratio gives the statistical weights of the components; at high concentrations a Boltzmann intensity ratio is obtained. The interpretation of the available optical data can be made to agree with the interpretation of ESR results by de Groot, Hesselmann, and van der Waals that a distorted 3B1u benzene is preferentially oriented in the site cavity of the solid phase, but the resulting picture is not a wholly satisfying one.
Second-Order Nuclear Dipolar Contribution to Second Moment of Integer Spins
Authors: Choy W. T. P. 
Published: January 2005

A formula has been derived for the second-order contribution of the dipolar broadening to the second moment of the resonance lines in pure quadrupole resonance experiments.
The following assumptions have been made: The nuclei undergoing the resonant transitions have spin ½; all resonant spins experience the same electric-field gradient which has a small amount of axial asymmetry; the dipolar interaction strength is small compared with the separation of the two resonance lines.
Deuteron Magnetic Resonance Study of Potassium Oxalate Monodeuterate
Authors: McGrath J. W. , Ossman G. W. 
Published: January 2005

Quadrupole splittings of the Larmor resonance for the deuteron in potassium oxalate monodeuterate (K2C2O4·D2O) were measured for single crystals at temperatures from −50° to 95°C. The D2O molecule is stationary at room and lower temperatures. The coupling constant and asymmetry parameter were determined to be 209.7±2.5 kc/sec and 0.090±0.020, respectively. The z field-gradient axis is within 4.8°±2.0° of parallelism with the O—D bond while the y axis is in the a—c plane and within 4.6°±2.0° of being perpendicular to the DOD plane.
The D2O molecule begins to 180° flip about its DOD bisector at 25°—50°C and higher. The coupling constant and asymmetry parameter of the flipping molecule are 114.2 kc/sec and 0.851, respectively. The z field-gradient axis is nearly perpendicular to the DOD plane while the y axis is nearly parallel to the D—D vector in its equilibrium position. Both axes are in the a—c plane and rotated away from perpendicularity and parallelism, respectively, by 4.6°±2.0°.
The coupling constants of this and three other deuterates differ among themselves and they are markedly lower than the computed and measured values for the isolated D2O molecule. Reasons for these differences are discussed including hydrogen bond strengths and D2O motion. For this crystal the field gradient due to nearby ions was estimated on the basis of a simple model and it was found to augment the measured coupling constant by about 9%.
Ternary Excess Enthalpies in Reciprocal Fused Salt Mixtures. IV. Effect of Charge Asymmetry
Authors: Meschel S. V. , Kleppa O. J. 
Published: January 2005

Calorimetric measurements have been carried out on the enthalpies of mixing in the reciprocal systems Cd2+–Ag+–Cl−–NO3− and Cd2+–Tl+–Cl−–NO3−. The results, when compared with corresponding data for the binaries and for the metathetical reactions, enable us to evaluate the ternary excess enthalpies. In order to give the results in a simple algebraic form we have adopted the concept of the equivalent enthalpy of mixing, and have expressed compositions in terms of equivalent ionic fractions.
It is found that the ternary excess enthalpies for the system Cd2+–Ag+–NO3−–Cl− may be accounted for by a suitable adaptation of the quasichemical theory. This suggests that these excess enthalpies largely are due to deviations from random mixing in the relative arrangement of cations and anions. However, for the system Cd2+–Tl+–NO3−–Cl− the ternary excess enthalpies show orders-of-magnitude deviations from the predictions of our adaptation of the quasichemical theory.
One-Center Study of the Rare-Gas Hydride Ions NeH+ and ArH+
Authors: Banyard K. E. , Sutton A. 
Published: January 2005

The ground states of the rare-gas hydride ions NeH+ and ArH+ have been studied by means of the united-atom (UA) treatment. Values are reported for the energy, theoretical bond length, force constant, and the diamagnetic part of the molar magnetic susceptibility. However, the present work is primarily intended as a test of the UA approach and, as such, it was useful to compare the results with those obtained by the same treatment for HF and HCl. Also, it proved to be most instructive to analyze the forces which act on the protons within each molecular ion.
As anticipated, the UA treatment of NeH+ and ArH+ met with meager success. Nevertheless, the analysis provided considerable understanding as to why a similar study, applied to neon- and argonlike molecules, yields fairly reasonable values for the above molecular properties when compared with experiment.
Cold-Neutron Study of Hindered Rotations in Solid and Liquid Methylchloroform, Neopentane, and Ethane
Authors: Rush J. J. 
Published: January 2005

The low-frequency modes of methylchloroform (1,1,1-trichloroethane), neopentane, and ethane in their solid and liquid phases have been investigated by the scattering of cold neutrons. The energy-gain spectra for these compounds in their low-temperature solid phases exhibit broad bands peaked at about 52, 50, and 82 cm−1 for CH3CCl3, C(CH3)4, and C2H6, respectively, which are attributed to whole-molecule librations and translations in the lattice. In the high-temperature phases of the ``globular'' compounds CH3CCl3 and C(CH3)4, these spectral bands are no longer peaked, but are quite diffuse and blend into a considerably broadened elastic peak. These results show that the phase transitions below the melting points are associated with a change from strongly hindered to quasifree rotation, in agreement with the results of previous experiments. The barrier to molecular reorientation is estimated to be ≲1 kcal/mole in the high-temperature phase of each compound.
Bands are also observed in the CH3CCl3 and C(CH3)4 spectra peaked at about 300 and 286 cm−1, respectively, which are assigned primarily to the torsional oscillations of the methyl groups. These peak positions show no significant change in proceeding from the liquid to the solid phases, indicating little intermolecular contribution to the forces hindering methyl-group reorientation. One of the liquid-ethane spectra exhibits a shoulder around 260 cm−1, which is possibly due to torsional vibrations. Assuming threefold cosine potentials with no interaction between methyl groups, ``average'' barriers to rotation of 5.8 and 5.2 kcal/mole are calculated from the torsional peaks for CH3CCl3 and C(CH3)4. The CH3CCl3 barrier is considerably higher than the value derived from thermodynamic results for CH3CCl3 (and ethane) gas.
Forbidden Transitions in Molecular Crystals: The Cameron System of Solid α-CO
Authors: Hexter R. M. 
Published: January 2005

A crystal splitting has been observed in the (0, 0) band of the Cameron system (a 3Π←X 1Σ+) of solid α-CO at 20°K, using a well-annealed sample. We believe that this is the first reported example of a triplet exciton splitting in a nonaromatic, the only previously reported examples having been in naphthalene and p-di-iodobenzene. A spin—orbit calculation has been carried out which demonstrates that the spectroscopic activity of this transition is primarily due to spin—orbit mixing of the 3Π1 and 1Π1 levels of the a 3Π and A 1Π states, respectively. The same calculation shows that the mixing of the ground and first triplet states can give intensity to this transition, but such intensity will be many times less than that induced via the first mechanism.
The electric-dipole character gained by the transition is insufficient to account for the observed splitting, i.e., as a Davydov splitting. Instead, it is concluded that molecules undergoing this transition are coupled via an intermolecular-exchange interaction. An estimate of the magnitudes of the exchange integrals in solid CO, relative to those in aromatic crystals, results in a prediction of a triplet exciton splitting for CO which is of the order of magnitude of the observed splitting. A vibronic interaction mechanism within the CO crystal may also account for the splitting. Experiments are discussed which can distinguish between the two coupling mechanisms and which can confirm one or the other as that responsible for the observed splitting.
Far-Infrared Spectra of Crystalline Benzene at 138°K and Intermolecular Forces
Authors: Harada Issei , Shimanouchi Takehiko 
Published: January 2005

Far-infrared spectra of crystalline benzene have been measured at low temperatures. The three bands assigned to the translational lattice vibrations have been found. The frequencies of these lattice vibrations, those of the Raman-active lattice vibrations and the frequency splittings of the infrared bands at 138°K have been consistently explained from the hydrogen—hydrogen and hydrogen—carbon interactions.
The values obtained for these atom—atom interactions are correlated with the values of other intramolecular and intermolecular force constants and with the energy of internal rotation for n-butane.
Ethylene Molecule in a Gaussian Basis. II. Contracted Bases
Authors: Schulman J. M. , Moskowitz J. W. , Hollister C. 
Published: January 2005

A self-consistent-field calculation on ground-state ethylene was performed using a large (sp) Gaussian basis. An upper bound to the Hartree—Fock energy and a lower bound to the correlation energy were obtained.
A SCF study was made using sets of ``contracted functions''—functions defined as linear combinations of Gaussians. It was found that orbital and total energies quite close to those of the large, straight Gaussian calculation can be obtained with contracted sets at a saving of computation time. These studies also furnished information about atomic-orbital input to be used in a LCAO orbital calculation.
Nitrogen-Isotope Effects in the Reduction of Nitrate, Nitrite, and Hydroxylamine to Ammonia. I. In Sodium Hydroxide Solution with Fe (II)
Authors: Brown L. L. , Drury J. S. 
Published: January 2005

Studies were made of the nitrogen-isotope effects occurring during the alkaline reduction of NO3−, NO2−, and NH2OH with Fe(II). The pertinent reduction reactions were shown to be irreversible and the yields of NH3 quantitative. The reduction of NO3− to NH3 produced a k14/k15 value of 1.075±0.004 at 25°C. A k14/k15 ratio of 1.034±0.002 at 25°C was obtained for the reduction of NO2−, or NH2OH to NH3. The rate constant, kNO3−, was shown to be slow compared to kNO2− and kNH2OH which had values of 4.09×10−2 and 9.53×10−3 sec−1, respectively.
The experimental data agreed well with results computed for a two-atom model in which the significant step in the reduction of each species was the breaking of an N–O bond. Reactions consistent with the experimental data were proposed to account for the reduction mechanism.
Hard-Sphere Lattice Gases. II. Plane-Triangular and Three-Dimensional Lattices
Authors: Gaunt David S. 
Published: January 2005

Exact low-density and high-density series are derived for the plane-triangular (pt) lattice gas, and in three dimensions, for the simple cubic (sc) and body-centered cubic (bcc) lattice gases, with first-neighbor exclusions. The series are studied by the ratio and Padé approximant extrapolation techniques. In all cases we find a continuous transition to an ordered state at the activities zt=11.05±15 (pt), 1.09±7 (sc) and 0.77±5 (bcc), and the densities ρt/ρ0=0.832±8 (pt), 0.427±20 (sc) and 0.355±20 (bcc). The grand potentials at these points are (pv0/kBT) = Γt=0.839±5 (pt), 0.380±10 (sc) and 0.290±15 (bcc). In all cases the uncertainties refer to the last decimal places.
The ordered state is characterized by a long-range order parameter which vanishes continuously and rapidly at the transition point. The transition is signed from above and below by the rapid divergence (faster than a simple pole) of the ``staggered compressibility.'' Apparently, the isothermal compressiibility also diverges to infinity from either side but with considerably less rapidity.
Normal, bound and nonbound testosterone levels in normally ageing men: results from the Massachusetts Male Ageing Study
Authors: Mohr Beth A. , Guay Andre T. , O'Donnell Amy B. , McKinlay John B. 
Published: January 2005

SummaryObjective  There is little consensus on what androgen levels are ‘normal’ for healthy, ageing men. Using data from the Massachusetts Male Ageing Study (MMAS), we estimated age‐specific, normal androgen levels for men aged 40–79 years while accounting for health status and behavioural factors known to influence hormone levels.Design  Prospective, observational study.Patients  Community‐based random sample of men aged 40–79 years: n = 1677 men studied at T1 (1987–1989), n = 1031 at T2 (1995–1997) and n = 631 at T3 (2002–2004), for a total of 3339 observations. The average number of years between the T1 and T2 interviews was 8·8 (range 7·1–10·4 years) and 6·4 (range 5·6–7·9 years) between T2 and T3.Measurements  Serum total testosterone (T) and sex hormone‐binding globulin (SHBG) were measured on nonfasting blood samples collected within 4 h of subject's awakening. Free and bio‐available T were calculated from T and SHBG using the Södergard equation. Trained interviewers administered an in‐home questionnaire of health, medication and lifestyle. Participants were considered apparently healthy if all of the following were met: (i) absence of self‐reported chronic disease (diabetes, heart disease, high blood pressure, cancer, ulcer); (ii) not on prescription medication believed to affect hormone levels; (iii) body mass index (BMI) not exceeding 29 kg/m2; (iv) alcohol consumption less than or equal to six drinks/day; and (v) nonsmoking.Results  Chronic disease and high BMI significantly decreased whereas smoking tended to increase total, free and bio‐available T concentrations. Apparently healthy men had significantly higher median hormone concentrations at most time points than did not apparently healthy men. Due to the opposite effects of smoking and the other components of the definition, apparently healthy men were compared to nonsmoking, apparently unhealthy men. The former group had significantly higher androgen levels (Wilcoxon rank‐sum P‐values ranged from 0·01 to 0·0001) for all hormones at all interviews. Ninety‐five percent of apparently healthy men in their 40s, 50s, 60s and 70s would be expected to have total T in the range (2·5–97·5th percentile): 8·7–31·7, 7·5–30·4, 6·8–29·8 and 5·4–28·4 nm (251–914, 216–876, 196–859, 156–818 ng/dl), respectively.Conclusions  Age, health and lifestyle factors impact androgen levels and should be accounted for in calculations of normal reference ranges. We propose the following age‐specific thresholds, below which a man is considered to have an abnormally low total T: 8·7, 7·5, 6·8 and 5·4 nm (251, 216, 196 and 156 ng/dl) for men in their 40s, 50s, 60s and 70s, respectively. These cutoffs correspond to the 2·5th percentile in our data; thus, approximately 2·5% of men aged 40–79 years would have abnormally low T levels based on hormone levels alone.