Robert E. LaVilla

K‐Absorption Fine Structures of Sulfur in Gaseous SF6

Measurements are reported on the K‐absorption fine structure of sulfur in gaseous SF6. The results differ qualitatively from previous measurements on molecular gases of lower coordination. Comparison is also made with preliminary results on H2S.

Carbon and fluorine x‐ray emission and fluorine K absorption spectra of the fluoromethane molecules, CH4−nFn(0 ≤ n ≤ 4). II

The carbon and fluorine Kα emission and the fluorine K absorption spectra of the molecular gases CH4−nFn(0 ≤ n ≤ 4) are reported. All the spectra were obtained on a single flat crystal spectrometer with photon counting. The emission spectra, which were excited by direct electron bombardment, are in fair agreement with an interpretation based on electric dipole transitions between single vacancy states and molecular orbital theory for the molecules. The applicability of x‐ray emission spectra to the determination of orbital order of a molecule is illustrated. The proximity of the resonance structure in the fluorine K absorption spectra for CH4−nFn(1 ≤ n ≤ 4) to their respective fluorine K shell thresholds suggests that the resonance structure is due to transitions to excited valence states 1a→ V* rather than Rydberg states.

Chlorine Kβ X‐Ray Emission Spectra from Several Chlorinated Hydrocarbon and Fluorocarbon Molecular Gases

Emission profiles have been obtained in x‐ray fluorescence for the four chlorinated derivatives of methane (CH3Cl, CH2Cl2, CHCl3, CCl4), and five chlorinated fluoromethanes (CF3Cl, CF2Cl2, CFCl3, CHFCl2, and CHF2Cl) in the gas phase. The chloromethanes contain two prominent lines whereas the chlorofluoromethanes have multiplet structures of up to four lines. Evidence is presented which suggests that these structures may be interpreted in terms of the molecular orbital term energies.

Molecular x‐ray spectra: S‐Kβ emission and K absorption spectra of SCO and CS2

The sulfur Kβ emission in fluorescence and K absorption of SCO and CS2 in gas/vapor phase were measured with a double crystal spectrometer. The sulfur Kβ emission spectra were compared with the complimentary x‐ray spectral data and with the MNDO and ab initio (STO‐3G) MO calculations and with previous larger basis set ab initio calculations. A comparison with the x‐ray spectra from CO2 was included for completeness. In addition the S‐1s binding energy was estimated for SCO and CS2 as 2478.7 and 2478.1 eV, respectively. Using the MO calculations as a guide, a tentative asssignment of the prominent features in the absorption spectra was made and compared with the S‐L2,3 absorption and energy loss spectra.

Molecular emission spectra in the soft X-ray region.

Spectra from several chlorine-containing hydrocarbon molecules excited to x-ray fluorescence have been recorded by a double crystal spectrometer with high resolving power. This study focuses on the region near the occurrence of the transition Kbeta(1,3) (1s(-1)-->3p(-1)) in chlorine. Whereas the free atom spectrum (from a single vacancy process) consists of an unresolved spin-orbit doublet, e.g., in argon, the molecular spectra often contain several lines. In free atom spectra and in molecular spectra also, there are extra lines or unresolved multiplets (satellites) due to multiple vacancy processes. In this report, these satellite lines are experimentally sorted out of the spectra and the remaining emission peaks associated with possible final state configuration containing a vacancy, i.e., the electronic terms of the molecule.

Gas Density Stabilizer for Flow Proportional Counters

A controller for gas density (pycnostat) is described with particular view to gain stabilization in flow proportional counters. The device is capable of operation at small flow rates and at pressures both above and below atmospheric. Constructional details and performance measurements are reported.

The sulfur Kβ emission and K‐absorption spectra from gaseous H2S. III

The sulfur Kβ emission in fluorescence and K absorption from gaseous H2S were measured on a double crystal spectrometer. The sulfur Kβ spectrum consists of four peaks. The three strongest peaks are shown to be single vacancy transitions of electrons from the three outer MO’s to fill the single K shell vacancy. The weak fourth peak on the high energy side of the three line structure is identified as a double vacancy transition. The sulfur K−absorption spectrum consists of three peaks of decreasing intensity with increasing photon energy. The unusual breadth (FWHM of 1.50 eV) and asymmetry on the high energy side of the first peak is ascribed to the Frank−Condon factors of the transitions to the unoccupied antibonding MO’s 3b2 and 6a1. The other two peaks, which are narrow, are identified as transitions to Rydberg levels. In addition, the binding energy of the sulfur K shell electron was estimated to be 2478.3 eV. The sulfur L2,3 absorption of H2S is also discussed briefly.

Detection of multiplet structure in Cu Kα1,2 by means of a monolithic double crystal spectrometer

Abstract A monolithic double crystal spectrometer has been employed to produce a highly dispersed, well-resolved Cu Kα 1,2 spectrum. The observed spectrum contains structure that can be attributed to spectator vacancies accompanying the single vacancy transition.

Molecular x‐ray spectra: S‐Kβ emission and K absorption spectra of thiophene

The high resolution sulfur Kβ emission in fluorescence and sulfur K absorption of thiophene (C4H4S) were measured with a double crystal spectrometer. The sulfur Kβ emission spectrum was analyzed by comparison with complementary spectral data and with MNDO and ab initio (STO‐3G) MO calculations. A tentative assignment of the prominent features in the absorption spectrum was made using MO calculations as a guide. In addition the sulfur LII,III emission spectrum was reinterpreted. The sulfur 1s binding energy of thiophene was estimated as 2477.6 eV.

Cl‐Kβ emission of chloromethanes and comparison with semiempirical and abinitio MO calculations

The chlorine Kβ emission in fluorescence from gas/vapor phase CCl4, CHCl3, CH2Cl2, and CH3Cl were measured with ‘‘good statistics’’ and previously undetected weak x‐ray emission features were observed. Results from ground state minimal and extended basis set ab initio (STO‐3G) and MNDO MO calculations for these molecules are presented. The chlorine Kβ emission spectra were analyzed by comparison with complementary spectral data and the MO calculations. In addition, weak features in Cl‐Kβ emission spectra resulting from self‐absorption in the sample were identified.