Spectra of H2–Ar, H2–Kr, and H2–Xe Van der Waals Complexes in Pressure-Induced Infrared Absorption

Spectra of H2–Ar, H2–Kr, and H2–Xe Van der Waals complexes, accompanying the Q1(0), Q1(1), S1(0), and S1(1) transitions of the pressure-induced fundamental infrared absorption band of hydrogen, have been studied in gas mixtures at 93–180 °K with a path length of 13 m and total pressures of ~3 atm. The main features of the spectra correspond to rotational transitions in the ground vibrational state of the complex, i.e., resolved T and N lines (Δl = ± 3) and unresolved R and P lines (Δl = ± 1), where l is the rotational quantum number of the complex. The spectra are analyzed with eigenvalues derived from the wave-mechanical solution of the isotropic Lennard–Jones 12–6 potential with constants determined from the combination rules for mixed molecular species. Although there is good overall agreement, it is evident that finer details of the spectra will require the introduction of an anisotropic intermolecular potential for their explanation.

Download Full-text

Spectra of H2–Ne and D2–Ne Van der Waals Complexes in the Collision-Induced Fundamental Bands of Hydrogen and Deuterium

Canadian Journal of Physics ◽

10.1139/p72-200 ◽

1972 ◽

Vol 50 (13) ◽

pp. 1458-1464 ◽

Cited By ~ 52

Author(s):

A. R. W. McKellar ◽

H. L. Welsh

Keyword(s):

Quantum Number ◽

Direct Evidence ◽

Van Der Waals ◽

Rotational Quantum Number ◽

Intermolecular Forces ◽

The Other ◽

Van Der Waals Complexes ◽

Intermolecular Potential ◽

Rare Gas ◽

Potential Well

Spectra of H2–Ne and D2–Ne Van der Waals complexes accompanying transitions in the collision-induced fundamental bands of hydrogen and deuterium have been obtained with an absorption path of 110 m at temperatures around 27 K in a specially designed multiple-traversal cell. The observed structure is similar to that of H2– and D2–Ar, Kr, and Xe complexes studied earlier, but the number of lines observed for the Ne complexes is fewer because of the shallower intermolecular potential. Well-resolved R and P branches (Δl= ±1, where l is the rotational quantum number of the complex) accompanying the overlap-induced Q1 (0) transitions are analyzed directly to give rotational (B) and centrifugal stretching (D) constants for the complexes. Unlike the other H2– rare gas complexes the spectra accompanying quadrupole-induced transitions show no direct evidence of anisotropy of the intermolecular forces.

Download Full-text

Spectra of (H2)2, (D2)2, and H2–D2 Van der Waals Complexes

Canadian Journal of Physics ◽

10.1139/p74-144 ◽

1974 ◽

Vol 52 (12) ◽

pp. 1082-1089 ◽

Cited By ~ 70

Author(s):

A. R. W. McKellar ◽

H. L. Welsh

Keyword(s):

Fine Structure ◽

Nuclear Spin ◽

Selection Rule ◽

Van Der Waals ◽

Rotational Quantum Number ◽

Van Der Waals Complexes ◽

Not Given ◽

Simple Effect ◽

Anisotropic Force ◽

Nuclear Spin Statistics

Spectra due to the Van der Waals complex (H2)2 have been obtained with greatly improved resolution, and analogous spectra of (D2)2 and H2–D2 have been observed. The experiments were conducted with an absorption path of 110 m in a multiple traversal cell at temperatures between 16 and 21 K. The spectra are manifested as fine structure accompanying the single and double H2 (or D2) transitions in the hydrogen (or deuterium) collision induced fundamental band. The observed structure for (H2)2 and H2–D2 can be unambiguously assigned to rotational transitions of the complex governed by the selection rule Δl = ± 1, ± 3, where l is the rotational quantum number of the complex. A detailed analysis must include anisotropic force effects, and is not given here. The spectrum of (D2)2 is complicated, not only by anisotropic force effects, but also by mutual perturbations between the rotational levels of the upper states of corresponding single and double D2 transitions; for this reason, the assignments suggested are somewhat uncertain. An interesting intensity alternation apparent in part of the (D2)2 spectrum is explained as a simple effect of nuclear spin statistics in the pseudodiatomic molecule (D2)2.

Download Full-text

J-Dependence of T2-Parameters for Rotational Transitions of SO2 and CH3OH in K-Band

Zeitschrift für Naturforschung A ◽

10.1515/zna-1985-0705 ◽

1985 ◽

Vol 40 (7) ◽

pp. 683-685 ◽

Cited By ~ 2

Author(s):

S. C. Mehrotra ◽

H. Dreizler ◽

H. Mäder

Keyword(s):

Fourier Transform ◽

Quantum Number ◽

Ground State ◽

Significant Variation ◽

Vibrational State ◽

Rotational Quantum Number ◽

Fourier Transform Spectrometer ◽

Ground Vibrational State ◽

Rotational Transitions ◽

Upper Level

With the help of a microwave Fourier transform spectrometer in the range from 18 GHz to 26 GHz, the coefficients ß for the linear pressure depedence of collisional dephasing rates 1/T2 have been determined by the transient emission technique for fourteen pure rotational transitions of SO2 with 5 ≦ J' ≦ 66 in the ground vibrational state, twelve transitions with 8 ≦ J' ≦ 62 in the first excited bending vibrational state, and twelve transitions of methanol with 2 ≦ J' ≦ 11, where J' is the rotational quantum number of the upper level of a transition. The T2-parameter ß for the transition J(K-, K+) - 49(4, 46 ) - 48(5, 43) of SO2 in the ground state shows an anomalous behaviour, whereas the values for all other transitions show a J-dependence in accordance with previous results. No significant variation of T2-parameters with J has been found for the rotational transitions of CH3OH.

Download Full-text