Theoretical study of the near uv photoabsorption by the Kr sub 2 * excimer

Technical Report · Sun Apr 01 04:00:00 EDT 1990

DOI:https://doi.org/10.2172/6851062· OSTI ID:6851062

Harvey, J F

The physical process responsible for near UV photoabsorption by the Kr*{sub 2} excimer are examined and the energy dependence of the photoabsorption cross sections is calculated. Near UV photoabsorption by the Kr*{sub 2} is a multiprocess phenomenon involving direct photoionization and concurrent photoexcitation to a repulsive resonance state, which subsequently autoionizes or dissociates. An adiabatic nuclei theory is developed, based on the use of Feshbach projection operators, to separate the ionization and dissociation channels, and to device photoionization and photodissociation cross sections. These cross sections are expressed in terms of parameters obtained from fixed nuclei electronic calculations and in terms wavefunctions describing nuclear motion. Stieltjes Tchebycheff Moment Theory (STMT) techniques are used to extract information concerning the ionization continuum from localized L{sup 2} electronic wavefunctions obtained from molecular electronic structure codes. Problems in the application of STMT techniques to narrow spectral features are examined. The cause of these problems is determined to be the use of the histogram midpoint approximation in low order STMT quadratures. Techniques are then developed which significantly improve the accuracy of STMT calculations for an isolated, narrow, resonance in a single continuum. Improved treatment of resonance profiles is demonstrated for pure Fano profiles, a shape resonance in a model barrier-and-well potential, and a shape resonance in the K-shell photoionization spectrum of N{sub 2}. The improved STMT techniques are then used to obtain the fixed nuclei resonance profiles in the spectrum of Kr{sub 2}.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• Sponsoring Organization: DOE/DP
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6851062
• Report Number(s): UCRL-LR-103555; ON: DE90011460
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
426002 -- Engineering-- Lasers & Masers-- (1990-)
640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
AUTOIONIZATION
COUPLING
CROSS SECTIONS
DISSOCIATION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCIMER LASERS
EXCITATION
EXCITED STATES
FLUIDS
FUNCTIONS
GAS LASERS
GASES
INTERMEDIATE COUPLING
IONIZATION
KRYPTON
L-S COUPLING
LASERS
MOLECULES
NONMETALS
OSCILLATOR STRENGTHS
PHOTOIONIZATION
RARE GASES
WAVE FUNCTIONS