Non-Franck--Condon 2sigma/sup -1//sub u/ vibrational distributions in N/sup +//sub 2/. An interchannel-coupled shape resonance observed by dispersed fluorescence
We report evidence for a molecular interchannel-coupled shape resonance in N/sub 2/ photoionization, observable in the vibrational branching ratios for the N/sup +//sub 2/(B /sup 2/..sigma../sup +//sub u/) state. The vibrational branching ratios for the N/sup +//sub 2/(B /sup 2/..sigma../sup +//sub u/) state are determined from vibrationally resolved dispersed fluorescence measurements on the N/sup +//sub 2/(B /sup 2/..sigma../sup +//sub u/..-->..X /sup 2/..sigma../sup +//sub g/) band system. The results demonstrate that the partial cross section for the N/sup +//sub 2/(B /sup 2/..sigma../sup +//sub u/,v' = 1) level is selectively enhanced in the photon energy range 28 <30 eV. A shape resonance occurs in this range for the 3sigma/sub g/..-->..epsilonsigma/sub u/ channel, and the observed enhancement is attributed to coupling between this channel and the 2sigma/sub u/..-->..epsilonsigma/sub g/ channel. Vibrational branching ratio curves for the excited state ion also show a pronounced peak at h..nu../sub exc/ = 22 eV, which shifts for the curves that sample the v' = 1 and v' = 2 levels of the ion, suggesting a few interpretations. The utility of coupling monochromatized fluorescence detection with synchrotron radiation excitation for extracting relative partial photoionization cross sections is demonstrated for the first time.
- Research Organization:
- Department of Chemistry, Boston University, Boston, Massachusetts 02215
- OSTI ID:
- 6008293
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 84:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NITROGEN
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
BRANCHING RATIO
ELECTRONIC STRUCTURE
SYNCHROTRON RADIATION
VIBRATIONAL STATES
BREMSSTRAHLUNG
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
EXCITED STATES
IONIZATION
NONMETALS
RADIATIONS
SPECTROSCOPY
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory