Resonance effects in the 5. sigma. sup minus 1 photoionization channel of CO

Journal Article · Fri May 15 04:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.462393· OSTI ID:7113706

Siggel, M R.F.; Hayes, M A; MacDonald, M A; West, J B ^[1]; Dehmer, J L ^[2]; Parr, A C; Hardis, J E ^[3]; Iga, I ^[4]; Tiit, V ^[5]

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1. Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom)
2. Argonne National Laboratory, Argonne, Illinois 60439 (United States)
3. National Institute for Standards and Technology, Gaithersburg, Maryland 20899 (United States)
4. Departamento de Quimica, Universidade Federal de Sao Carlos, Via Washington Luiz 13560 (Brazil)
5. Institute of Physics, 202400 Tartu (Estonia)

Vibrational branching ratios and photoelectron angular distributions are reported for the 5{sigma}{sup {minus}1} photoionization channel of CO in the range 16 eV{lt}{ital h}{nu}{lt}45 eV. Striking non-Franck--Condon effects are observed in both the branching ratios and angular distributions as a result of various autoionizing states and a {sigma} shape resonance that lie in this spectral range. The goal of the present measurement was to observe definitive evidence for the {sigma} shape resonance via its non-Franck--Condon effects on the vibrational ionization channels. Guided by recent calculations (Smith, Lynch, and McKoy, J. Chem. Phys. {bold 85}, 6455 (1986)), we examined the broad structure in the vibrational branching ratios and angular distributions in the range 25 eV {lt}{ital h}{nu}{lt}40 eV. There, we found clear evidence for the {sigma} shape resonance in the quantities {beta}({ital v}{sup +}=0 and 1) and {sigma}({ital v}{sup +}=2)/{sigma}({ital v}{sup +}=0). Substantial differences between theory and experiment for the {sigma}({ital v}{sup +}=1)/{sigma}({ital v}{sup +}=0) branching ratio, however, serve to define the limitations of the current single-channel picture for this process.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7113706
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 96:10; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ANGULAR DISTRIBUTION
AUTOIONIZATION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
DISTRIBUTION
ENERGY LEVELS
EXCITED STATES
FRANCK-CONDON PRINCIPLE
IONIZATION
OXIDES
OXYGEN COMPOUNDS
PHOTOIONIZATION
RESONANCE ABSORPTION
SORPTION
VIBRATIONAL STATES