Double-resonance spectroscopy of the high Rydberg states of HCO. III. Multiple pathways in the vibrational autoionization of the bending overtone

Journal Article · Fri May 01 04:00:00 EDT 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476270· OSTI ID:627896

Mayer, E E; Hedderich, H G; Grant, E R ^[1]

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1. Department of Chemistry, Purdue University, West Lafayette, Indiana47907 (United States)

Ultraviolet first-photon absorption selects individual rotational levels in the Renner{endash}Teller split (020) vibronic band system in the 3p{pi}{sup 2}{Pi} Rydberg state of HCO. These gateway states serve as originating levels for vertical second-photon transitions to vibrationally autoionizing Rydberg series converging to individual rotational levels associated with the (02{sup 0}0) and (02{sup 2}0) states of HCO{sup +}. Linewidths of assigned series convey information on autoionization dynamics. Resonances throughout the (020) autoionization spectrum match sharp profiles seen earlier for series converging to HCO{sup +}(010). Linewidths for autoionization via relaxation both of the bending fundamental and its overtone are measurably narrower than resonances built on CO stretch, (001), which indicates that mode-selectivity inhibiting bending autoionization relative to stretch extends to the bending overtone. Features in the (020) spectrum that fall below the threshold energy for decay by autoionization to the (010) continuum appear with diminished intensity and yet narrower linewidth. This provides evidence that vibrational autoionization in HCO conforms with a {Delta}v=1 propensity rule that favors relaxation of (020) states to the (010) continuum over the two-quantum decay to produce HCO{sup +}(000). Analysis of detailed line shapes and intensities associated with individual vibrational angular momentum components of the relaxing-core overtone point to the way in which vibrational and orbital-electronic symmetries factor in the bound molecule and cation plus free electron, and fix the order in vibrational coordinates of necessary coupling terms. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 627896
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 20 Vol. 108; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ABSORPTION SPECTRA
AUTOIONIZATION
DOUBLE RESONANCE METHODS
ELECTRONIC STRUCTURE
FORMYL RADICALS
HARMONICS
LINE WIDTHS
ROTATIONAL STATES
RYDBERG STATES
ULTRAVIOLET SPECTRA
VIBRATIONAL STATES