Photoexcitation and ionization in molecular fluorine: Stieltjes--Tchebycheff calculations in the static-exchange approximation

Journal Article · Tue Jan 15 04:00:00 EST 1980 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.439187· OSTI ID:5542646

Orel, A E; Rescigno, T N; McKoy, B V; Langhoff, P W

Theoretical investigation of outer (1..pi../sub g/, 1..pi../sub u/, 3sigma/sub g/) and inner (2sigma/sub u/, 2sigma/sub g/) valence-shell electronic photoexcitation and ionization cross sections in molecular fluorine are reported employing separated-channel static-exchange calculations and Stieltjes--Tchebycheff (S--T) moment-theory techniques. The discrete vertical electronic 1..pi../sub g/ excitation series are found to be in good agreement with recent spectral assignments and previously reported theoretical studies, and those for 1..pi../sub u/, 3sigma/sub g/, 2sigma/sub u/ and 2sigma/sub g/ excitations are in general accord with position and intensity estimates based on quantum-defect analysis. Certain of the partial-channel photoionization cross sections in F/sub 2/ are seen to exhibit resonancelike features similar to those reported recently in related S--T studies of photoionization in N/sub 2/, CO, and O/sub 2/. The resonances can be attributed to valencelike and pre-Rydberg diabatic states that cross the outer limbs of appropriate Rydberg series and corresponding ionic-state potential curves as functions of internuclear coordinate, giving rise to large continuum transition intensities at the ground-state equilibrium internuclear separation. In contrast to the situation in N/sub 2/, CO, and O/sub 2/, however, there is no evidence of a resonance like sigma..-->..sigma* feature in the 3sigma/sub g/..-->..ksigma/sub u/ photoionization channel in F/sub 2/. Rather, this resonance in F/sub 2/ appears as a strong N..-->..V/sub g/ transition below the 3sigma/sub g/ ionization threshold, and the corresponding partial-channel photoionization cross section is seen to be structureless.

• Research Organization: Theoretical Atomic and Molecular Physics Group, Lawrence Livermore Laboratory, University of California, Livermore, California 94550
• OSTI ID: 5542646
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 72:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
CROSS SECTIONS
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUORINE
HALOGENS
IONIZATION
NONMETALS
PHOTOIONIZATION