Resonance enhanced multiphoton ionization photoelectron spectra of CO[sub 2]. III. Autoionization dominates direct ionization

Journal Article · Mon Feb 01 04:00:00 EST 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.464215· OSTI ID:6817988

Taylor, D P; Johnson, P M ^[1]

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1. Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400 (United States)

In (3+1) resonance enhanced multiphoton ionization photoelectron spectra (REMPI-PES) of CO[sub 2], photoionization competes with dissociation. In addition to direct photoionization, autoionization is possible through accidental resonances embedded in the continuum at the four-photon level. Photoabsorption from these long-lived autoionizing states leads to resonance enhanced above threshold absorption (REATA). REATA produces photoelectron terminations on the [ital [tilde C]] state of CO[sub 2][sup +]. Previous experiments did not indicate whether the dissociation occurred at the three-photon level or four-photon level. REMPI-PES of CO[sub 2] via several Rydberg states have been collected at a number of laser intensities, and it was found that the photoelectron spectra terminating on each individual ionic state do not change over the range of experimentally available laser intensities. This indicates that the dissociation of CO[sub 2] occurs at the four-photon level. The long vibrational progressions in the PES indicate that the dominant ionization process is autoionization rather than direct ionization. Relative intensities of the [ital [tilde X]] and [ital [tilde C]] state components of the PES do change with intensity, confirming the [ital [tilde C]] state assignment and its five-photon mechanism.

• DOE Contract Number: FG02-86ER13590
• OSTI ID: 6817988
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 98:3; ISSN JCPSA6; 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
AUTOIONIZATION
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
ENERGY LEVELS
EXCITED STATES
IONIZATION
MULTI-PHOTON PROCESSES
OXIDES
OXYGEN COMPOUNDS
PHOTOIONIZATION
RESONANCE
RYDBERG STATES
VIBRATIONAL STATES