Gordon L. Goodman

Raman Spectra of MoF6, TcF6, ReF6, UF6, SF6, SeF6, and TeF6 in the Vapor State

Raman spectra of MoF6, TcF6, ReF6, UF6, SF6, SeF6, and TeF6 have been observed for the gaseous state using laser excitation. Some assignments of fundamental frequencies have had to be revised from previously accepted values. The overtone 2ν6 was observed for all these gaseous hexafluorides and several other overtones were observed for some of the molecules. Considerable broadening of the eg and f2g fundamentals was observed for TcF6 and for ReF6. This broadening is attributed to dynamic Jahn–Teller coupling. The best currently available measured values of fundamental frequencies for all 15 hexafluoride molecules of known Oh symmetry are tabulated.

Spectral Observations on Molecular XeF6: Raman Scattering and Infrared, Visible and Ultraviolet Absorption in the Vapor and in Matrix Isolation

Raman spectra and visible and ultraviolet absorption spectra of XeF6 vapor have been studied as functions of temperature. The changes that occur in the observed spectra are interpreted as due to relative population changes of the three electronic isomers postulated in the preceding paper. Evidence is presented that, even at temperatures as high as 100°C, it may take tens of minutes to reach equilibrium among the isomers. Infrared spectra of both XeF6 vapor at 25°C and of XeF6 molecules isolated in a low temperature argon matrix have been studied for a variety of previous thermal treatments of the XeF6 samples. In the spectra of the matrix, large differences in the relative intensities of absorption bands were found, depending on the thermal history of the XeF6 used in the deposition. All the spectra observed are interpreted in terms of the three electronic isomers, and the assignments appear quite plausible.

Precise determination of the v and N dependence of the spin-rotation and hyperfine interactions in the CaF X2Σ12 ground state☆☆☆

Abstract The molecular-beam, laser-rf, double-resonance technique has been used to make high-precision measurements of both the v and N dependences of the spin-rotational and hyperfine splittings in the X 2 Σ 1 2 ground state of CaF. The precision (1 ppm) and scope (1 ≤ N ″ ≤ 119, 0 ≤ v ″ ≤ 4) of the data allow evaluation of many of the parameters (with the Dunham expansion) in the Hamiltonian. The results are compared with new ab initio calculations.

PES of higher temperature vapors: Lithium halide monomers and dimers

The He (I) photoelectron spectra of ’’pure’’ monomers and dimers of the lithium halides have been obtained by using a double‐oven technique to vary the dimer:monomer ratio. The lithium halide monomer spectra conform nicely to a model based on spin–orbit and ligand field interactions previously introduced. The first ionization potentials of the dimers are in each case higher than in the corresponding monomers. These conclusions are also deduced in this paper by ionic model calculations and molecular calculations of the X‐α type, using the discrete variational method. The X‐α calculations enable us to assign tentatively the dimer valence bands. These calculations have been extended to trimer and tetramer structures and indicate an oscillation in the first ionization potential in the series encompassing monomer through tetramer. Some experimental verification exists up to trimer. The oscillatory behavior is also obtained in a crude ionic model calculation. An experimental method using photoionization mass sp...

Infrared and Raman Spectra of Krypton Difluoride

The infrared and Raman spectra of KrF2 vapor have been obtained. They clearly indicate a linear and symmetric molecule with the symmetric stretching frequency at 449 cm−1, the asymmetric stretching frequency at 588 cm−1, and the bending frequency at 232.6 cm−1. The force constants are fr=2.46, frr=−0.20, and fα=0.21 mdyn/A. The negative bond—bond interaction constant can be explained neither by valence bond models nor by a simple molecular orbital model.

Hyperfine and spin–rotational structure of CaBr X 2Σ (v = 0) by molecular‐beam laser‐rf double resonance

The molecular‐beam, laser–rf, double‐resonance technique has been used to make high‐precision measurements of the spin–rotation and hyperfine interactions in the X 2Σ (v = 0) electronic ground state of Ca79Br and Ca81Br. The spin–rotation interaction is found to have a strong N dependence. The Frosch–Foley magnetic hyperfine parameters b and c and the electric–quadrupole hfs parameter eqQ are determined for both molecules.

Electronic States and Molecular Geometry of Xenon Hexafluoride: A Case of Electronic Isomerism

It is proposed that XeF6 vapor is a mixture of three molecular isomers differing primarily in electronic state and nuclear geometry. The lowest energy form is octahedrally symmetric and has two anti‐bonding electrons in an a1g orbital, yielding a 1A1g electronic state. The first excited states arise from promoting one of the anti‐bonding electrons to a f1u orbital. For an octahedral nuclear geometry this produces a 3F1u electronic state, which however is subject to Jahn‐Teller distortion forces. These forces lead to a D3d molecular symmetry and two separate electronic states 3A2u and 3Eu. The 3A2u state is about 450 cm−1, and the 3Eu state about 1200 cm−1 above the ground state. Because of high statistical weights, these excited states are well populated at the temperatures usually used for physical measurements, and any detailed interpretations of data must take this into account.

Photoelectron spectroscopy of AgCl, AgBr, and AgI vapors

He I photoelectron spectra of AgCl, AgBr and AgI vapors have been obtained which differ significantly from earlier work. In each instance, the characteristic features of the diatomic molecule are prominent. The spectral features separate into a valence region, predominantly halogen p‐like, and a deeper region, predominantly of Ag 4d character. The latter is split by spin–orbit and ligand field interactions, which are parametrized from the experimental data. Relativistic calculations of the Xα–DVM–SCC type have been performed for these species. At the transition state level, they agree very well with the experimental peak positions. Nonrelativistic calculations of this type have been performed for CuCl and cyclic Cu3Cl3. Unlike the AgX species, the CuCl and Cu3Cl3 exhibit strong mixing of metal d and halogen p orbitals for the uppermost occupied orbital, and other Cu 3d‐like orbitals above the Cl 3p‐like orbitals. It is suggested that the occurrence of Cu 3d orbitals in the valence region may play a role i...

High-precision laser and rf spectroscopy of the spin-rotation and hfs interactions in the X2Σ+ and B2Σ+ states of LaO

Abstract The spin-rotation and hyperfine interactions in the X2Σ+ and B2Σ+ electronic states of 139La16O have been studied using Doppler-free laser-induced fluorescence and molecular-beam laser-rf double resonance. Observations were made for several values of v and many values of N, allowing evaluation of the principal interaction strengths and their N and v dependences for both the X and B states. The results are compared with earlier results for the isoelectronic system 137Ba19F.

Partial photoionization cross sections of atomic iodine; irreducible tensor analysis of intensities

The He i photoelectron spectrum of atomic iodine has been obtained from a thermal source. The relative intensities are compared with recent data on Cl and Br. The major difference is an inversion in the relative intensities of 3P0 and 1S0 between Cl and I. An intermediate coupling angular momentum treatment, combined with spectroscopic mixing parameters, reproduces this inversion quantitatively, and, in addition, adequately describes the entire intensity pattern for all three halogens. The strong implication is that angular factors and mixing parameters are the dominant features in determining relative intensities, and radial integrals and ’’anisotropic electron–ion interactions’’ are much less important.