Kenneth Fox

Measurement and analysis of the infrared‐active stretching fundamental (ν3) of UF6

High‐resolution spectra of the infrared‐active stretching fundamental ν3 of 238UF6 have been obtained between 620.6 and 633.5 cm−1 using tunable semiconductor diode lasers. Interference from hot bands was suppressed by cooling the UF6 in a supersonic expansion, and useful monomer concentrations were produced with effective temperatures of <100 K. Portions of the band from P(77) to R(66) are illustrated. All transitions from the vibrational ground state have been assigned, and the Q branch has been fully analyzed. A total of 43 line frequencies and 110 frequency differences extending in J to P(77), Q(91), and R(67) has been used to fit seven spectroscopic constants. The ground‐ and excited‐state values of the rotational constant B could be individually determined, and the U–F bond length in the ground vibrational state is r0=1.9962±0.0007 A. The Q branch of 235UF6 has also been analyzed and the 235UF6–238UF6 ν3 isotope shift measured to be 0.603 79±0.000 17 cm−1. The isotope shift and the Coriolis constant...

Variational Calculation for Bound States in an Electric‐Dipole Field

The quantum‐mechanical problem of an electron moving in the field of a permanent electric dipole has been investigated in an attempt to determine whether negative energy eigenvalues, i.e., bound states, exist for small dipole moments. When the expectation value of the Hamiltonian is minimized in a variational calculation and then set equal to zero, the solution of the resulting equation gives a value of the dipole moment which is sufficient to assure the existence of a bound state. Use of the trial wavefunction ψ=exp (—αrt) (C0Y00+C1Y10) shows that 1.65×10−18 esu·cm is sufficient.

Calculated linewidths for CH4 broadened by N2 and O2

The Anderson‐Tsao‐Curnutte theory of collision‐broadened spectral lines, as extended by Tejwani for octopolar interactions, has been used to compute linewidths for methane broadened by molecular nitrogen and oxygen. Widths of vibration‐rotation lines in the infrared‐active fundamental bands ν2, ν3, and ν4; the combination bands ν2 + ν3 and ν3 + ν4; and the overtone bands 2ν3, 2ν4, and 3ν3 have been calculated for the symmetry species A, E, and F separately, and for a large range of the total angular momentum quantum number J. The effect of the dipole moment of CH4 due to vibration‐rotation interactions was considered. The temperature dependence of the linewidths has been obtained for 210°K ≤ T ≤ 300°K. These results were used to compute corresponding air‐broadened linewidths. It has been shown that the calculated linewidths depend significantly on the magnitude of the octopole moment for methane.

High resolution spectroscopy of the OsO4 stretching fundamental at 961 cm−1

The ν3 bands of 187Os16O4, 189Os16O4, and 192Os16O4 have been recorded using both a Michelson interferometer (resolution 0.06 cm−1) and a tunable semiconductor diode laser (resolution limited by the Doppler width, ∼0.0007 cm−1). The rotational fine structure differs from that of most other spherical‐top molecules, for only rotational levels of A symmetry exist. A total of 112 individual vibration–rotation lines in the P and R branches of the three isotopic species were calibrated against stimulated emission lines from a high‐voltage CO2 gain cell, and were used to determine three scalar and two tensor spectroscopic constants for each species; an additional scalar constant was obtained from an analysis of the Q branch of 192OsO4. The strength of P (11) A2 0 was measured for 192OsO4 and yields a vibrational transition moment for ν3 of 0.17±0.02 D. Transitions of all isotopic species that are expected to fall near CO2 laser lines in the region 949–972 cm−1 are tabulated as an aid in the interpreation of satu...

Collision-broadened linewidths of tetrahedral molecules—II. Computations for CH4 lines broadened by N2, O2, He, Ne and Ar☆

Pressure-broadened widths of CH4 lines have been calculated, using the recent formulation for tetrahedral molecules by Varanasi in the framework of the Anderson-Tsao-Curnutte theory. The present work deals mainly with lines of the R-branch of the ν3-fundamental at 300°K, for the range 1≤J≤30 and 0≤K≤18, and for the F species. In the case of CH4-N2 and CH4-O2 collisions, octopole-quadrupole, octopole-hexadecapole, hexadecapole-quadrupole, hexadecapole-hexadecapole, dispersion and overlap interactions have been included. Broadening by noble gases was treated in terms of dispersion and overlap interactions. The value |ΩCH4|=2·25×10−34 esu cm3 obtained in the present work by comparing theoretical and experimental results for γ0CH4−N2 is not far from the magnitude deduced in studies of the far-i.r. collision-induced absorption spectra of methane. A magnitude for the hexadecapole moment of |ΦCH4|=3·0×10−42 esu cm4 was also determined. The calculated and measured linewidths are in good agreement, except in CH4-Ar collisions. In the latter case, the theoretical values are appreciably lower than the experimental ones, which suggests that induced interactions may have to be included.

Calculated self‐ and foreign‐gas‐broadened linewidths for CH3D

Self‐, N2−, O2−, and H2− broadened linewidths for CH3D have been calculated using the Anderson‐Tsao‐Curnutte theory. Interactions due to the dipole and octopole moments of CH3D were included. Linewidths have been computed for a wide range of angular momentum quantum numbers J and K, and temperature dependence has been obtained for 100 ≤ T ≤ 300°K.

High-resolution infrared spectrum and analysis of the ν9 band of ethane at 12.17 μm

Abstract The ν9 degenerate fundamental of C2H6 near 12.17 μm (822 cm−1) has been recorded at medium resolution (Δν = 0.125−0.500 cm−1) and high resolution (Δν = 0.04−0.05 cm−1) using both grating and interferometric spectrometers. The spectra have been assigned and analyzed by both standard and band contour techniques. The high-resolution spectrum showed a pronounced l-doubling in the K = 0 subband and the presence of a (2,2) type l-resonance. The assigned lines were corrected for these effects and analyzed using an energy expression through third order ( h 3 † ) with partial fourth-order ( h 4 † ) contributions. The standard deviation for the analysis of 549 of 569 assigned transitions was 6.7 × 10−3 cm−1. The ν9 band has been observed recently on Jupiter, Saturn, Titan, and Neptune by several workers. Spectra, frequency listings, and assignments have been included for use in future work on C2H6 in the atmospheres of the outer planets.

Rotational energy for spherical tops. II. Triply‐degenerate fundamental

The Hamiltonian for a triply‐degenerate fundamental of spherical top molecules is extended to sixth order of approximation. Formulas for the energy levels are given.

Spectra of van der Waals complexes (dimers) with applications to planetary atmospheres

Abstract We have attributed spectral features observed in the atmosphere of Titan by the Voyager i.r. experiment to weakly bound complexes of N 2 and H 2 , dominant and minor constituents, respectively. We have also computed the abundance of H 2 -N 2 dimers there. Our current calculations include quantitative spectral line positions and intensities for N 2 -Ar and CO 2 -CO 2 relating to Titan and Earth, and to Mars and Venus, respectively. This work suggests applications to spectra of planetary atmospheres obtained in spacecraft missions.

Measurements of nitrogen-, hydrogen- and helium-broadened widths of methane lines at 9030–9120 cm-1

Pressure-broadened widths of vibration-rotation lines of both 12CH4 and 13CH4 have been measured at very high spectral resolution in the R-branch of the 3ν3 overtone. The broadening gases were N2, H2 and He, as well as a mixture of H2 and He. Results are presented as averages for J-multiplets at ambient temperature. The overall R-branch values for line widths in 12CH4-N2, 12CH4-H2, 12CH4-He, 12CH4-H2+He and 13CH4-H2 are 0.0711 ± 0.0064, 0.0687 ± 0.0030, 0.0429 ± 0.0012, 0.0545 ± 0.0030 and 0.0678 ± 0.0054 cm-1 atm-1, respectively.