Single-photon spectroscopy of singlet sulfur atoms and the autoionization lifetime measurements of the superexcited singlet states
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616 (United States)
Single-photon excitation spectra from the lowest singlet {sup 1}D{sub 2} level of sulfur atoms were recorded with a tunable vacuum ultraviolet (VUV) radiation source generated by frequency tripling in noble gases. The photolysis of CS{sub 2} at 193 nm was used to produce the singlet S({sup 1}D{sub 2}) sulfur atoms that were then excited to neutral superexcited states with the tunable VUV radiation. These superexcited states undergo autoionization into the first ionization continuum state of S{sup +}({sup 4}S{sub 3/2}{sup o})+e{sup -}, which is not directly accessible from the S({sup 1}D{sub 2}) state via an allowed transition. The excitation spectra were recorded by monitoring the S{sup +} signal in a velocity imaging apparatus while scanning the VUV excitation wavelength. Three new lines were observed in the spectra which have not been previously reported. The full widths at half maximum (FWHM) of each of the observed transitions were determined by fitting the profiles of each absorption resonances with the Fano formula. Autoionization lifetimes {tau} of these singlet superexcited states were obtained from FWHM using the Uncertainty Principle. Abnormal autoionization lifetimes were found for the 3s{sup 2}3p{sup 3}({sup 2}D{sup o})nd({sup 1}D{sub 2}) and the 3s{sup 2}3p{sup 3}({sup 2}D{sup o})ns({sup 1}D{sub 2}) Rydberg series, in which {tau}(5d) and {tau}(7s) are shorter than {tau}(4d) and {tau}(6s), respectively. This is contrary to the well-known scaling law of {tau}(n*){proportional_to}n*{sup 3}, which should be followed within a series unless there exist perturbations from other series or new channels open up to which some members of the series can decay. Possible perturbations from the nearby triplet series are suspected for causing the broadening of the 5d and 7s levels.
- OSTI ID:
- 20662339
- Journal Information:
- Journal of Chemical Physics, Vol. 122, Issue 14; Other Information: DOI: 10.1063/1.1875032; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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