bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermophysical properties of the lanthanide sesquisulfides. III. Determination of Schottky and lattice heat-capacity contributions of γ-phase Sm2S3 and evaluation of the thermophysical properties of the γ-phase Ln2S3 subset
Authors: Shaviv Roey , Westrum Edgar F. , Gruber John. B. , Beaudry B. J. , Palmer P. E.
Published: July 2002

We report the experimental heat capacity of γ-phase Sm2S3 and derived thermophysical properties at selected temperatures. The entropy, enthalpy increments, and Gibbs energy function are 21.50R, 3063R⋅K, and 11.23R at 298.15 K. The experimental heat capacity is made up of lattice and electronic (Schottky) contributions. The lattice contribution is determined for all γ-phase lanthanide sesquisulfides (Ln2S3 ) using the Komada/Westrum model. The difference between the experimental heat capacity and the deduced lattice heat capacity is analyzed as the Schottky contribution. Comparisons are made between the calorimetric Schottky contributions and those determined based on crystal-field electronic energy levels of Ln3+ ions in the lattice and between the Schottky contributions obtained from the empirical volumetric priority approach and from the Komada/Westrum theoretical approach. Predictions for the thermophysical properties of γ-phase Eu2S3 and γ-phase Pm2S3 (unavailable for experimental determination) are also presented.
Water self-diffusion in lyotropic systems by simulation of pulsed field gradient-spin echo nuclear magnetic resonance experiments
Authors: Celebre Giorgio , Coppola Luigi , Ranieri Giuseppe Antonio
Published: July 2002

In this paper the pulsed field gradient-spin echo nuclear magnetic resonance (PFG-SE) experiment has been performed by computer simulation technique. The diffusive phenomenon is reproduced by letting particles, moving only by Brownian motion, travel among reflecting aggregates; in such a way it is possible to calculate the nuclear magnetic resonance (NMR) echo attenuation due to the solvent self-diffusion in lyotropic systems overcoming the problem of the analytical determination of the probability distribution of the spins. The results obtained on lamellar and inverted hexagonal lyomesophases are in good agreement with the previous functions reported in literature and new results are given for the hexagonal phase treated using this approach; in particular a new interpolation formula for the determination of the obstruction factor as a function of the structural parameters is proposed.
Formation of the chelate bonds in the cluster O−2(CO2)n, CO−3(CO2)n, and NO−2(CO2)n
Authors: Hiraoka Kenzo , Yamabe Shinichi
Published: July 2002

The equilibria of gas-phase clustering reactions of O−2, CO−3, and NO−2 with CO2 were studied with a pulsed electron beam high-pressure mass spectrometer. Thermochemical stabilities of the clusters O−2(CO2)n, CO−3(CO2)n, and NO−2(CO2)n with n=1–8 were determined. For O−2(CO2)n, irregular decreases in the values of −ΔH0n−1,n were observed between n=1 and 2, and n=3 and 4. These gaps indicate that the bond with covalent character is formed through the charge transfer (CT) O−2→CO2 and the CT complex of O2COO− accommodates two CO2 molecules preferably [i.e., O2COO−(CO2)2]. The −ΔH0n−1,n values of both CO−3(CO2)n and NO−2(CO2)n clusters show an irregular decrease between n=4 and 5. This suggests the formation of shells, OCO−2(CO2)4 and NO−2(CO2)4. Ab initio optimized geometries of these clusters are found to be composed of bridge (i.e., chelate) intermolecular bonds.
Turbidity of deuterated isobutyric acid and heavy water in the one-phase region near the critical solution point
Authors: DaMore Lori W. , Jacobs D. T.
Published: July 2002

We have measured the total light scattered from a mixture of deuterated isobutyric acid and heavy water (deuterium oxide, D2O ) near its upper critical solution point. The resulting turbidity was measured in a reduced temperature region 10−6<t<10−2, where t=(T−Tc)/Tc and Tc is the critical solution temperature, in a sample close to the critical composition. This completely deuterated mixture near its critical point exhibits similar properties to the undeuterated mixture and the turbidity can be explained using an Ising model. When the critical exponents ν and γ were fixed at the values predicted from renormalization-group theory, the amplitude ξ0 of the correlation length was determined to be 0.343±0.024 nm, while the amplitude of the turbidity τ0 was (3.51±0.03)×10−6 cm−1, which seem consistent with two-scale-factor universality predictions.
Formation, stability, and structure of helium hydrate at high pressure
Authors: Londono David , Finney John L. , Kuhs Werner F.
Published: July 2002

Neutron powder diffraction experiments show that, in the presence of ice and at helium-gas pressures exceeding 0.28 GPa, a gas hydrate with the composition He(6+x)H2O is formed. Its host lattice closely resembles that of ice II. However, the stability range of the helium hydrate is considerably more extended as compared to that of ice II: helium hydrate melts and recrystallizes from the liquid and is more stable than ice III/IX or ice V, at least up to 0.5 GPa. The helium content increases with increasing-pressure/decreasing-temperature, but does not appear to follow an ideal solution behavior, as do the guests in some heavier noble-gas clathrates. The lattice parameters of helium hydrate are significantly different from those of ice II, while the atomic arrangement of the host lattice is very similar, showing full orientational order of the water molecules.
Optical–optical double resonance multiphoton ionization spectroscopy of ammonia-d3. II. Jahn–Teller effect and related Fermi resonance of the B̃ 1E″ state
Authors: Li Xiaonong , Xie Xingbin , Li Li , Wang Xiaotian , Zhang Cunhao
Published: July 2002

By selecting a number of resonant Ã 21 rotational lines in the optical–optical double resonance multiphoton ionization spectroscopy (OODR-MPI) of ammonia-d3, we have obtained rotationally resolved spectra of the ND3 B̃←Ã 21←X̃ 00 transitions in the range of 550–730 nm, in which not only were we able to reanalyze rotationally the previously studied bands [J. Opt. Soc. Am. B 7, 1884(1990)], but also to assign rotationally and vibronically some novel spectra pertaining to the ν1, ν3, ν4, and ν3+ν4 excitations. Based on the symmetry assignment and the relationship of the vibronic coupling level energies between the single and dual mode cases, we have found that the Jahn–Teller splitting of the ND3 B̃ state invokes a novel type of the Fermi resonance, the nonadiabatic Fermi resonance. By taking account of this Fermi resonance, the modified vibronic coupling parameters of the ν3 and ν4 modes were calculated to be λ3=0.047 and λ4=0.023, which agrees well with the previous theoretical expectation that the ammonia B̃ state is subject to a mild dynamic Jahn–Teller effect. At present, four pairs of the nonadiabatic Fermi resonance have been discovered among the ND3 nonadiabatic levels, which can be separated into two types—one with the same selection rules as a conventional Fermi resonance, i.e., B̃ 31(1/2)–B̃ 42(5/2), B̃ 11–B̃ 42(1/2), and B̃ 31(3/2)–B̃ 42(3/2), the last of which was studied quantitatively with a coupling parameter K=114, and the other with novel selection rules, i.e., B̃ 31(1/2)–B̃ 11.
Thermodynamic formula for the reversible work of forming a noncritical cluster from the vapor in multicomponent systems
Authors: Nishioka Kazumi , Mori Atsushi
Published: July 2002

A thermodynamic formula is derived for the reversible work of forming a noncritical liquid cluster from the vapor in multicomponent systems. It is found that the commonly used formula may be used but, for a given state of the parent vapor phase, the value of the surface tension for the critical nucleus must be used in the surface term even if the surface tension of a noncritical cluster may differ significantly from that of the critical nucleus due to the differences in the composition and the size.
Predicting observables on different potential energy surfaces using feature sensitivity analysis: Application to the collinear H+H2 exchange reaction
Authors: Chang Johnny , Brown Nancy J. , D’Mello Michael , Wyatt Robert E. , Rabitz Herschel
Published: July 2002

Two sensitivity-analysis techniques are used to show how one can predict observables on new or perturbed potential energy surfaces (PES) without doing any additional dynamics calculations on the new PESs. Both techniques require the computation of the observable (O) and its sensitivity to variations in the potential (δO/δV) on just one surface. The first approach uses a simple first order expansion of the observable with respect to δV. The second approach uses a nonlinear least-squares fit of particular features in the observable, and then uses the same functional form to predict the observable on a different PES but with a modified set of fitting parameters. The new fitting parameters are related to the old via a functional Taylor expansion. Both approaches work well when variations in the potential are small. When the potential difference is large, the second approach gives reasonable results even in cases where the first approach is giving spurious predictions. These ideas are tested for the collinear H+H2 reaction within the framework of quantum reactive scattering. The log-derivative version of the Kohn variational principle is used for the scattering calculations.
Probing the evanescent field of propagating plasmon surface polaritons by fluorescence and Raman spectroscopies
Authors: Knobloch H. , Brunner H. , Leitner A. , Aussenegg F. , Knoll W.
Published: July 2002

Flourescence and Raman scattering intensities have been measured for different probe molecules positioned at various defined separation distances from a Ag grating carrying a propagating plasmon surface polariton mode. Thus, the evanescent decay length of such a surface–electromagnetic wave could be mapped out, and was found to agree with theoretical predictions based on a Fresnel formalism.
Linear response Fano–DeVoe polarizability theory for biopolymers composed of chiral chromophores: Infinite order dipole–dipole approximation calculations of circular dichroism and ultraviolet band shapes of α-helical and β-pleated polypeptides
Authors: Ito Hirotoshi , Arakawa Yuuji , I’Haya Y. J.
Published: July 2002

The first order dimer model made by Stiles and Buckingham for predicting optical activity has been extended up to an infinite order N-mer model within the framework of the Fano–DeVoe type dipole approximation. The present formalism involves four mechanisms (1) the Kirkwood–Moffitt coupled oscillator mechanism through the Coulombic interactions; (2) the local asymmetric mechanism due to the intrinsic monomer optical activity; (3) the indirect electric–magnetic coupling mechanism through the Coulombic interactions; (4) the Condon, Alter, Eyring (CAE) direct electric–magnetic coupling mechanism through the electrostatic interactions between the upper to upper state transition moments on a certain site and the permanent dipole moments on the other sites. However, mechanism (4) must be excluded if we follow the Fano–DeVoe approximation, whereas it is indispensable for circular dichroism (CD) calculations of polypeptides to incorporate the CAE electric–magnetic coupling mechanism. This requirement is attained by assuming the intra-amide monomer intensity borrowing of the very weak 210 nm region nπ* state from the strong 190 nm region ππ* state through the CAE electrostatic interactions on the basis of the Schellman–Oriel perturbation equation and the Bayley–Nielsen–Schellman secular matrix theory. The present theory has particularly well predicted the CD band shapes of α-polypeptides even with the dipole approximation. The contributions due to the asymmetric fields have been found to become specifically large, while the coupled oscillator mechanism has been calculated to be a leading term.
Mobilities and interaction potentials for the O+–He and O−–He systems
Authors: Viggiano A. A. , Morris Robert A. , Mason E. A.
Published: July 2002

Mobilities of O+ and O− ions in He gas have been measured as a function of electric field strength at temperatures from 93 to 568 K. The results are compared with previous work, and analyzed in terms of a temperature-field strength scaling rule and the O+–He and O−–He potentials. Emphasis is placed on how much information on the potentials can be obtained from simple features of the mobility curve without extensive numerical computation.
Adiabatic representations for the study of flux redistribution during photodissociation involving coupled electronic states: The effect of vibrational excitation on the photofragmentation of CH3I
Authors: Rist Claire , Alexander Millard H.
Published: July 2002

In this paper we exploit a method for the time-independent study of the growth of photofragment flux, governed by photon absorption, and the subsequent redistribution of the flux, governed by the Hamiltonian in the excited, unbound state. For dissociation involving multiple electronic states, each with internal (vibrational or rovibrational) degrees of freedom, from a mechanistic standpoint it is more revealing to analyze the flux in a basis which is adiabatic in the nuclear degrees of freedom but diabatic in the electronic degrees of freedom. This approach is pursued here in application to a two-dimensional model for the photodissociation of CH3I.
Comment on: Electron–ion recombination rate constants in gaseous and liquid krypton
Authors: Mozumder A.
Published: July 2002

A comment on recombination rate constant in liquid and gaseous krypton is presented. The problem is addressed from the point of re− encounter theory. (AIP) E
A spectroscopic and theoretical analysis of the internal rotation bands appearing in the S1–S transition of phenylsilane
Authors: Ishikawa Haruki , Kajimoto Okitsugu , Kato Shigeki
Published: July 2002

The laser-induced fluorescence excitation spectra of phenylsilane near the 0–0 transition have been observed and analyzed in terms of the torsional (internal rotational) motion of the silyl group. The rotational constants of phenylsilane in the excited state were also determined. The high-resolution spectrum of the 0–0 band shows a unique profile, which consists of an ordinary b-type profile and a central peak. The rotational contour analysis showed that the band consists of two overlapping torsional bands of a b-type transition. From the analysis including the rotational structure of the torsional bands, the potential barrier was determined to be 45.0 cm−1, which is much higher than that of toluene (27.0 cm−1). The large difference in the barrier height between toluene and phenylsilane reflects a difference in the electronically excited states of these compounds. An ab initio molecular orbital calculation was carried out to get an insight into the nature of the electronically excited phenylsilane. The calculated structures in both the S1 and S0 states are in good agreement with the observed ones. The interaction between the silyl group and the π system turned out to be due to hyperconjugation with the Si–H antibonding orbital, and the interaction with vacant d-orbitals of the Si atom is not significant.
Pure rotational spectra of the mixed rare gas van der Waals complexes Ne–Xe, Ar–Xe, and Kr–Xe
Authors: Jäger Wolfgang , Xu Yunjie , Gerry M. C. L.
Published: July 2002

Pure rotational transitions in the vibrational ground states of various isotopomers of the heteronuclear rare gas dimers Ne–Xe, Ar–Xe, and Kr–Xe have been measured using a pulsed molecular beam cavity microwave Fourier transform spectrometer. Rotational and centrifugal distortion constants have been obtained, and have yielded estimates of the lengths of the van der Waals bonds and of their harmonic vibration frequencies. Effects due to nuclear quadrupole coupling have been observed in 131Xe-containing complexes and have yielded the corresponding nuclear quadrupole coupling constants. The electric molecular dipole moments of the complexes have been estimated from the excitation pulse lengths, optimized for maximum signal strength (π/2 condition).
Molecular dynamics with combined quantum and empirical potentials: C2H2 adsorption on Si(100)
Authors: Carmer C. S. , Weiner B. , Frenklach M.
Published: July 2002

Classical trajectory calculations were employed to study the reaction of acetylene with dimer sites on the Si(100) surface at 105 K. Two types of potential energy functions were combined to describe interactions for different regions of the model surface. A quantum mechanical potential based on the semiempirical AM1 Hamiltonian was used to describe interactions between C2H2 and a portion of the silicon surface, while an empirically parametrized potential was developed to extend the size of the surface and simulate the dynamics of the surrounding silicon atoms. Reactions of acetylene approaching different sites were investigated, directly above a surface dimer, and between atoms from separate dimers. In all cases, the outcome of C2H2 surface collisions was controlled by the amount of translational energy possessed by the incoming molecule. Acetylene molecules with high translational energy reacted with silicon dimers to form surface species with either one or two Si–C bonds. Those molecules with low translational energy either rebounded away from the surface or became trapped in a physisorbed state as evidenced by their bouncing motion above the surface. The reaction of C2H2 to form a bridge between dimers within the same dimer row was found to occur, while bridging between adjacent dimer rows appeared to be unlikely, the C2H2 molecule preferring to migrate to either of the dimers for direct reaction. A mechanism is proposed for chemisorption in which C2H2 first bonds to a dimer site in a mono-σ structure, subsequently attaining the more stable di-σ bonded state through radical–radical recombination. The simulations are consistent with C2H2 adsorption on Si(100) occurring through a mobile precursor mechanism.
Anion formation from gaseous and condensed CF3I on low energy electron impact
Authors: Oster Tatiana , Ingolfsson Oddur , Meinke Martina , Jaffke Thomas , Illenberger Eugen
Published: July 2002

Anion formation following electron impact to CF3I is studied in the energy range 0–15 eV. The experiments include gas phase CF3I in the effusive molecular beam under single collision conditions, clusters in a supersonic molecular jet and CF3I condensed in the UHV in multilayer amounts onto a cold metallic substrate. In isolated molecules fragment anions are formed via dissociative attachment (DA) and dipolar dissociation (DD). The DA resonances are located at 0.0 and 3.8 eV and are assigned as single particle and two particle resonance, respectively. The low energy resonance exhibits an exceedingly high cross section for I− formation, while the higher energy resonance decomposes into CF3−, F−, and FI− with comparatively low intensity. Both resonances possess significant C–I antibonding character as apparent from their decomposition dynamics. In clusters the stabilized molecular anion CF3I− and larger complexes of the form (CF3I)n− and (CF3I)n⋅I− are observed. At higher energies anion formation is affected by inelastic scattering from one molecule and capture of the slow electron by a second molecule within one cluster (self-scavenging). Scavenging features in clusters and in isolated molecules beyond single collision conditions are compared. Electron stimulated desorption (ESD) is dominated by CF3− which is generated via DA from the core excited resonance with its strong F3C–I antibonding nature.
The role of solvent intramolecular modes in excess electron solvation dynamics
Authors: Murphrey Tim H. , Rossky Peter J.
Published: July 2002

The role played by solvent molecular flexibility in the dynamics of the solvation of an initially energetically excited excess electron in water is investigated using nonadiabatic molecular dynamics simulation and a classical flexible water model. It is found that the effect of flexibility on relaxation times is substantial, but the effect on the branching ratio for excess electrons passing through alternative intermediate excited states is small. Examination of the optical absorption spectra of the hydrated electron shows that the effect of solvent flexibility is also small here. An analysis of transient spectra supports the validity of a kinetic analysis based on species with individual well defined signatures. However, the data suggest that a two state analysis of the dynamics neglects a potentially important role for early time delocalized electrons.
Sensitivity of the F+H2 reaction probability to the potential surface
Authors: Lazarides A. A. , Neuhauser D. , Rabitz H.
Published: July 2002

The method of functional sensitivity analysis is used to identify the areas of reactive significance on the T5A potential. The influence of various regions of the potential upon the total integrated reaction probability of F+H2(v=0,j=1) is examined for collision energies in the range 0.032–0.066 eV and for total angular momentum J=5 and 10. Several regions are identified as having particularly strong influence on the reaction probability at these energies. The most influential region is, as expected, the saddle point and the approaching slope. The HF(v′=3) adiabatic exit barrier region and the region between the saddle point and the exit barrier are also confirmed to be important. While upward adjustments of the potential in either of the barrier regions would lower the predicted probability of reaction, increasing the potential in the interbarrier region would raise the reaction probability. Among nearly collinear arrangements, the inner wall of the exit valley, which includes the effective turning point at the end of the entrance valley, exerts a surprisingly large influence on the reaction probability. Implications of these results for refinement of the potential are discussed.
Dehydrogenation reactions in Mg+(H2O)n clusters
Authors: Harms A. C. , Khanna S. N. , Chen B. , Castleman A. W.
Published: July 2002

Experimental observations of the effects of solvation on the dehydrogenation reaction of Mg+(H2O)n to produce MgOH+(H2O)n−1 are presented for n≤6. The reaction is seen to occur spontaneously at room temperature for n≳4. Ligand switching reactions are used to show the Mg+–OH bonds are stronger than Mg+H2O bonds. The results show the energy required to lose an H atom decreases with the number of water molecules attached because the magnesium changes oxidation state and this results in stronger interactions with the water ligands. Ab initio calculations are used to explain these observations.
Ab initio predictions of the structures and spectra of some simple thiosulfeno (XS2) free radicals
Authors: Zhuo Q. , Clouthier Dennis J. , Goddard John D.
Published: July 2002

Ab initio theory with split-valence plus polarization function and larger basis sets at the self-consistent field (SCF) and second order Mo/ller–Plesset (UMP2) levels was used to predict the geometries and spectroscopic parameters for the ground and first excited electronic states of the HS2, FS2, and ClS2 free radicals. The ground-state species are predicted to be bent and may be described as having a sulfur–sulfur double bond, a sulfur-substituent single bond, and an unpaired electron which is delocalized principally over the sulfur centers. The first electronic transition involves an (n,π*) electron promotion which leads to a longer S–S bond, smaller bond angle, and greater localization of the unpaired electron on the terminal sulfur atom. The adiabatic transition energies are predicted to be at ∼6700, 13 700, and 10 600 cm−1 for HS2, FS2, and ClS2, respectively. The theoretical results are in good agreement with the rather limited amount of experimental data available. These ab initio predictions provide critical information to aid in future experimental studies of the matrix isolation or gas-phase spectra of the thiosulfeno radicals.
Sign of V6 term in internal rotation potential of acetaldehyde. Theory and experiment in harmony
Authors: Goodman Lionel , Leszczynski Jerzy , Kundu Tapanendu
Published: July 2002

The V6 term, regulating the shape of the internal rotation potential for a single rotor, has been predicted by ab initio theory for acetaldehyde. The internal rotation potential constants were computed by single point fourth order Mo/ller–Plesset (MP4) 6-311G(3df,2p) level theory for three models differing in molecular flexing motions using MP2 optimized molecular geometries. The negative sign of V6, established by microwave and infrared experiments, is predicted only by the fully relaxed model which includes out-of-plane wagging of the aldehyde hydrogen. This requires strong coupling of methyl torsional motion to the hydrogen wag. The predicted magnitude of V6 differs by only 4 cm−1 from the experimentally established value.
365 nm photon-induced dynamics of ClNO adsorbed on MgO(100)
Authors: Ferkel H. , Hodgson L. , Singleton J. T. , Blass P. M. , Reisler H. , Wittig C.
Published: July 2002

Temperature programmed desorption (TPD) and 365 nm photolysis of ClNO adsorbed on MgO(100) at 90 K were investigated under ultrahigh vacuum conditions. The crystal was treated in a way that largely eliminated oxygen vacancies and yielded a relatively smooth surface. Angularly resolved time-of-flight (TOF) mass spectra and state-selective resonance-enhanced multiphoton ionization (REMPI) spectra of NO photoproducts were obtained. The TPD data indicate that ClNO desorbs at surface temperatures above 160 K for exposures (Θ) below 0.2 Langmuirs (L), while for higher values of Θ the main desorption peak is near 120 K. The higher temperature feature, which saturates at Θ∼0.3 L, is probably associated with binding to defect sites. Thermal desorption is believed to be molecular at all coverages. Irradiation at 365 nm for 0.1≤Θ≤5.0 L yields products having low average translational energies and broad translational energy distributions. NO fragment REMPI spectra were recorded at Θ≥0.7 L. The rotational distributions could be fit with a temperature of 110±10 K, i.e., comparable to that of the substrate. These results differ from those obtained in the photodissociation of gas-phase ClNO, where the NO fragment has high translational and rotational energies. However, the present results are similar to those obtained on rougher MgO(100) surfaces. Possible mechanisms are discussed.
Evidence for quantization of the transition state for cis–trans isomerization
Authors: Choi Young S. , Kim Taek-Soo , Petek Hrvoje , Yoshihara Keitaro , Christensen Ronald L.
Published: July 2002

Cis–trans isomerization rates of trans,trans-1,3,5,7-octatetraene (OT) on the first excited singlet state (2 1Ag) potential surface have been obtained as a function of vibrational energy by measuring the fluorescence lifetimes. A stepwise increase in the isomerization rate with increasing energy has been observed, which indicates quantization of the vibrational levels of the transition state for the cis–trans isomerization of a double bond. The energy spacing of 80±10 cm−1 between the first two steps tentatively is assigned to an in-plane bending vibration of the transition state.
Integral equation theory of block copolymer liquids. II. Numerical results for finite hard-core diameter chains
Authors: David Edwin F. , Schweizer Kenneth S.
Published: July 2002

The spatially local and long wavelength properties of diblock copolymer melts are studied using the polymer reference interaction site model theory. Two new molecular based closure approximations, the ‘‘reference-molecular mean spherical approximation’’ (R-MMSA) and the ‘‘reference-molecular Percus–Yevick’’ (R-MPY) approximation are investigated numerically for structurally symmetric, flexible, and semiflexible copolymers with finite hard-core diameters. For these models both closures lead to a destruction of all spinodal instabilities for finite degrees of polymerization. Results using the R-MMSA closure for the larger chain lengths studied approach the analytic predictions of the Gaussian thread model. On the other hand, numerical results for the R-MPY closure show a temperature regime in which there is an apparent chain length independent fluctuation stabilization for moderate degrees of polymerization in qualitative agreement with recent Monte Carlo simulations. However, we believe this apparent scaling arises from a very slow approach towards the asymptotic, finite size fluctuation behavior analytically derived in the previous paper for the Gaussian thread model. In accord with recent simulations, the peak scattering wave vector exhibits temperature dependence due to collective, many chain fluctuation effects. Predictions of the local structure and composition in the disordered phase are made which show that considerable length scale dependent deviations from homopolymer melt packing emerge at low temperatures.
Calculation of the rovibrational B←X excitation spectrum of the He2Cl2 cluster
Authors: Hernández Marta I. , Halberstadt Nadine
Published: July 2002

Three-dimensional quantum mechanical calculations on the rovibrational B←X excitation spectrum of He2Cl2 are presented, and give excellent agreement with recent experiments. It is also shown that the spectrum can be fit by a rigid rotor if He exchange symmetry and overlapping He–He bending excitations are taken into account.
Influence of chain stiffness on the micellization of block copolymers in a selective solvent as observed in Monte Carlo simulations
Authors: Adriani Paul , Wang Yongmei , Mattice Wayne L.
Published: July 2002

The micellization in a selective solvent of a diblock copolymer with blocks of different stiffness is studied with Monte Carlo simulation on a cubic lattice. When the stiffness of the insoluble block increases, the critical micelle concentration (cmc) decreases and the averaged micelle size increases. On the other hand, an increase in the stiffness of the soluble block does not affect the micellization process to any appreciable extent. The decrease in the cmc when the stiffness of the insoluble block increases is interpreted as arising from the conformational contribution to the effective χ parameter. We interpret this contribution as being due to an increased number of heterocontacts between the insoluble block and the solvent molecules when the stiffness of the insoluble block increases.