Journal of Chemical Physics
1089-7690
0021-9606
Mỹ
Cơ quản chủ quản: American Institute of Physics , AIP PUBLISHING
Lĩnh vực:
Medicine (miscellaneous)Physical and Theoretical ChemistryPhysics and Astronomy (miscellaneous)
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Thông tin về tạp chí
The Journal of Chemical Physics publishes quantitative and rigorous science of long-lasting value in methods and applications of chemical physics. The Journal also publishes brief Communications of significant new findings, Perspectives on the latest advances in the field, and Special Topic issues. The Journal focuses on innovative research in experimental and theoretical areas of chemical physics, including spectroscopy, dynamics, kinetics, statistical mechanics, and quantum mechanics. In addition, topical areas such as polymers, soft matter, materials, surfaces/interfaces, and systems of biological relevance are of increasing importance. Topical coverage includes: Theoretical Methods and Algorithms Advanced Experimental Techniques Atoms, Molecules, and Clusters Liquids, Glasses, and Crystals Surfaces, Interfaces, and Materials Polymers and Soft Matter Biological Molecules and Networks.
Các bài báo tiêu biểu
Vibrational Spectra and Structure of Four-Membered Ring Molecules. III. Bromocyclobutane, Bromocyclobutane-<i>d</i>1, Bromocyclobutane-<i>d</i>4, and Bromocyclobutane-<i>d</i>5 The infrared spectra of bromocyclobutane, α-bromocyclobutane-d1, β,β,β′,β′-bromocyclobutane-d4, and α,β,β,β′,β′-bromocyclobutane-d5 in both the liquid and vapor phases have been recorded from 4000 to 250 cm−1. The far-infrared spectra of bromocyclobutane and β,β,β′,β′-bromocyclobutane-d4 have been recorded to 33 cm−1. The Raman spectra of the four isotopic species of bromocyclobutane in the liquid state have also been recorded and depolarization values have been measured; the carbon—bromine stretching region of bromocyclobutane-d1 has been scanned at temperatures varying from 35° to −83°C. The spectra have been interpreted by considering the molecules as having one plane of symmetry and belonging to point group Cs. Frequency assignments which are based on group-frequency correlations, isotopic shifts, depolarization values, band contours, and relative intensities where applicable are given for the normal vibrations. The assignments are tabulated and discussed according to symmetry species. The regimens of the product and noncrossing rules have been followed. Support for the existence of ``equatorial'' and ``planar'' conformers is presented and the nature of the potential function governing the ring-puckering vibration for bromocyclobutane is discussed.
Tập 47 Số 2 - Trang 673-691 - 1967
Spectra and Structure of Small Ring Compounds. XIX. Vibrational Analysis and the Barrier to Pseudorotation of Germylcyclopentane The infrared spectrum of germylcyclopentane in the gaseous state has been recorded from 4000 to 33 cm−1 and that of 1, 1-dideutero-1-germylcyclopentane has been recorded from 4000 to 250 cm−1. The Raman spectra of the two liquids have been recorded and depolarization values determined. The data rule out the planar configuration for the germylcyclopentane molecule and are shown to be consistent with the twisted C2 molecular structure. The 39 normal modes have been assigned on the basis of their depolarization values, infrared band contours, isotopic shift factors, band intensities, and “group frequencies.” The ring-bending mode was found at 113 cm−1 in the vapor phase of the “light” compound. The ring-twisting mode for the d0 and d2 compounds was found at 273 and 269 cm−1, respectively, in the Raman spectrum. The 113-cm−1 band in the light compound was found to be the first of a series of Q branches running to lower frequency. This series has been interpreted in terms of a relatively high barrier to pseudorotation. From midinfrared sum bands a similar series of transitions were obtained for the pseudorotation of the d2 compound. A potential function of the form V = − (2043 / 2) (1 − cos2θ) − (21 / 2) (1 − cos6θ) was found to fit nine observed far-infrared transitions of the ring-puckering mode. The calculated barrier to pseudorotation was 5.9 ± 0.1 kcal/mole for the “light” compound, and the spectroscopically derived parameter mq02 was found to be 18.7 × 10−40 g·cm2. The barrier in the corresponding d2 compound is estimated to be 6.0 ± 0.3 kcal/mole. The barriers are considerably higher than one might expect from existing theories and data on torsional barriers.
Tập 52 Số 12 - Trang 6108-6119 - 1970
Vibrational Spectra and Structure of Small-Ring Compounds. X. Spectroscopic Evidence for Pseudorotation in Cyclopentane The infrared spectrum of cyclopentane has been examined from 33 to 4000 cm−1. A series of pronounced Q branches with a 5-cm−1 spacing was observed on top of the CH2 deformation. The Q branch frequencies could be reproduced by assuming that the cyclopentane ring was undergoing pseudorotation. The spectroscopically derived parameter mq02 was found to be (11.0 ± 0.2) × 10−40 g·cm2.
Tập 49 Số 5 - Trang 2118-2121 - 1968
Spectra and structure of small ring compounds. XXXVII. Two-dimensional potential surface and barrier to interconversion for silacyclopentane The Raman spectrum of gaseous silacyclopentane has been recorded from 25 to 4000 cm−1. The series of Q branches observed at 264.5, 259.9, and 255.3 cm−1 have been assigned as the fundamental and hot bands of the radial vibration of a hindered pseudorotator. A two-dimensional potential surface has been determined and indicates that the interconversion between equivalent twisted forms proceeds through a puckered intermediate. The barrier of 1414 cm−1 is of the same order as that found using a one-dimensional treatment, and the two models are discussed.
Tập 67 Số 10 - Trang 4756-4759 - 1977
Spectra and Structure of Small Ring Compounds. XX. Fluorocyclobutane The infrared spectrum of fluorocyclobutane vapor has been recorded from 4000–33 cm−1. The infrared spectrum of the solid at − 196°C has been recorded from 4000–200 cm−1. The Raman spectra of the liquid at room temperature and the solid have been recorded and depolarization values have been measured. The spectra have been interpreted on the basis of a puckered model ring with only one conformation which has a plane of symmetry and belongs to the Cs point group. Assignment of the 30 normal vibrations has been based on depolarization values, band contours, group-frequency correlations, and relative intensities. A series of four Q branches was observed in the far-infrared spectrum and has been interpreted as arising from the fundamental and “upper-state” transitions of the anharmonic ring-puckering vibration. The series could be fit equally well by two different double-minima potential functions, one with a relatively high barrier of 803 cm−1 and the other with a 485-cm−1 barrier. On the basis of previous microwave data and the midinfrared and Raman spectra of the solid and fluid states, the higher barrier potential is believed to more nearly describe the actual potential function governing the ring-puckering vibration; the energy difference between the two conformations was calculated to be 722 cm−1.
Tập 54 Số 4 - Trang 1547-1556 - 1971
The microwave spectrum of the equatorial conformer of chlorocyclopentane The microwave spectrum of chlorocyclopentane has been reinvestigated. The ground state and two vibrationally excited states of the equatorial conformation of c-C5H935Cl have been identified. The ground state rotational constants are A=6424.51(14) MHz, B=1832.304(6) MHz, C=1523.163(5) MHz. The spectrum of the 37Cl substituted species has also been assigned. For the previously reported axial conformer of c-C5H935Cl, additional transitions have been measured in the ground state and the first excited state of the lowest frequency motion and the spectrum of another vibrationally excited state has been assigned. The experimental rotational constants have been used to derive plausible molecular structures for both conformers. The experimental quadrupole coupling constants are compatible with the proposed structures.
Tập 94 Số 5 - Trang 3315-3321 - 1991
Raman spectra of gases. VI. Barrier to planarity in germacyclopentane The anharmonic out-of-plane twisting mode of the heavy atom skeleton of germacyclopentane has been observed in the Raman spectrum of the vapor. These data along with the far infrared frequencies for the other out-of-plane ring bending mode have made it possible to calculate the two-dimensional potential surface for these two out-of-plane ring modes without any assumptions as to the magnitude of the barrier to planarity. From this two-dimensional treatment, it is shown that the interconversion between the two twisted configurations is not entirely along the twist axis but the path is actually slightly elliptical and passes through a slightly bent configuration at R2=0. However, it is shown that the twisting and puckering motions are fairly independent. From the two-dimensional treatment, one calculates the barrier to interconversion to be ∼ 1450 cm−1 compared to the less accurate value of 2043 cm−1 calculated using the one-dimensional approximation.
Tập 58 Số 6 - Trang 2393-2396 - 1973
Vibrational Spectra and Structure of Four-Membered Ring Molecules. II. Chlorocyclobutane, Chlorocyclobutane-<i>d</i>1, and Chlorocyclobutane-<i>d</i>4 The infrared spectra of chlorocyclobutane, α-chlorocyclobutane-d1, and β,β,β′,β′-chlorocyclobutane-d4 in both the gaseous and liquid states have been recorded from 4000 to 250 cm−1. The far-infrared spectrum of β,β,β′,β′-chlorocyclobutane-d4 in the vapor state has been recorded down to 33 cm−1. The Raman spectra of the three isotopic species of chlorocyclobutane have also been recorded of the liquid phases and depolarization values measured. The spectra have been interpreted by considering the molecule to have a plane of symmetry and belonging to point group Cs. Assignment of the frequencies of the fundamental vibrations is based on position, isotopic shift, band type, and depolarization values. The ring-puckering vibration in chlorocyclobutane was observed in the Raman spectrum at 165 cm−1, and found at 159 cm−1 in the far-infrared spectrum of the vapor. The data shows that the first upper-state transition of the ring-puckering vibration is centered at 142 cm−1. For the tetradeuterated molecule the ring-puckering vibration was found at 144 cm−1 in the far-infrared spectrum of the vapor. The nature of the potential energy function governing the ring-puckering vibration is discussed.
Tập 46 Số 12 - Trang 4854-4868 - 1967
Physical Adsorption on Non-Uniform Surfaces Analysis of adsorption on a uniform surface using the quasi-chemical theory of interaction shows that the hypotheses of the BET theory lead to substantially no adsorption beyond the first layer if E2 = EL, and stepwise isotherms if E1>E2>E3>···>EL. For the monolayer adsorption of gases on silver, platinum, and steel, the heterogeneous nature of the adsorbing surface is clearly indicated. Cooperative adsorption on the non-uniform surface is treated, and the cooperative analog of the Freundlich equation derived. The typical multi-layer isotherm is shown to be composed of three regions: non-cooperative adsorption on a strongly heterogeneous surface; cooperative adsorption on a still heterogeneous surface; and cooperative multi-layer adsorption induced by small van der Waals perturbations some distance from the surface.
The isotherm p/p0=exp{—a/θr} is derived and shown to be a good representation of adsorption data that conform to the BET Type I, II, or III shapes.
Tập 16 Số 10 - Trang 931-937 - 1948