Rotationally resolved pulsed field ionization photoelectron study of CO[sup +](X[sup 2][Sigma][sup +],v[sup +]=0[endash]42) in the energy range of 13. 98[endash]21. 92 eV

Journal Article · Mon Nov 01 00:00:00 EST 1999 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.480259· OSTI ID:5903350

Evans, M; Ng, C Y ^[1]

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1. Ames Laboratory, USDOE and Department of Chemistry, Iowa State University Ames, Iowa 50011 (United States)

We have obtained rotationally resolved pulsed field ionization[endash]photoelectron (PFI-PE) spectra of CO in the energy range of 13.98[endash]21.92 eV, covering the ionization transitions CO[sup +](X hthinsp;[sup 2][Sigma][sup +],v[sup +]=0[endash]42,N[sup +])[l arrow]CO(X hthinsp;[sup 1][Sigma][sup +],v[sup [double prime]]=0,N[sup [double prime]]). The PFI-PE bands for CO[sup +] hthinsp;(X hthinsp;[sup 2][Sigma][sup +], v[sup +]=8[endash]22, 24, and 28[endash]39) obtained here represent the first rotationally resolved spectroscopic data for these states. The high-resolution features observed in the PFI-PE spectra allow the identification of vibrational bands for the CO[sup +] hthinsp;(X hthinsp;[sup 2][Sigma][sup +], v[sup +]=10, 14, 15, 17, 18, 21, 24, 25, 29[endash]31, 33, 35[endash]37, and 39) states, which strongly overlap with prominent vibrational bands of the CO[sup +](A hthinsp;[sup 2][Pi][sub 3/2,1/2],B hthinsp;[sup 2][Sigma][sup +]) states. The simulation using the Buckingham[endash]Orr[endash]Sichel model has provided accurate molecular constants for CO[sup +](X hthinsp;[sup 2][Sigma][sup +],v[sup +]=0[endash]42), including ionization energies, vibrational constants ([omega][sub e][sup +]=2218.8[plus minus]3.5 hthinsp;cm[sup [minus]1], [omega][sub e][sup +]x[sub e][sup +]=16.20[plus minus]0.32 hthinsp;cm[sup [minus]1], [omega][sub e][sup +]y[sub e][sup +]=0.074[plus minus]0.011 hthinsp;cm[sup [minus]1], and [omega][sub e][sup +]z[sub e][sup +]=[minus]0.001 hthinsp;83[plus minus]0.000 hthinsp;13 hthin p;cm[sup [minus]1]), and rotational constants [B[sub e][sup +]=1.9797[plus minus]0.0051 hthinsp;cm[sup [minus]1], [alpha][sub e][sup +]=0.0201[plus minus]0.0011thinspcm[sup [minus]1], [gamma][sub e][sup +]=0.000 hthinsp;122[plus minus]0.000 hthinsp;067 hthinsp;cm[sup [minus]1], z[sub e][sup +]=[minus](5.2[plus minus]1.1)[times]10[sup [minus]6] hthinsp;cm[sup [minus]1]]. Enhancement of [Delta]N[lt]0 rotational branches, attributable to field-induced rotational autoionization, was clearly discernible in PFI-PE bands for CO[sup +] hthinsp;(X hthinsp;[sup 2][Sigma][sup +], v[sup +]=0[endash]5, 11, and 12). Significant local enhancements due to near-resonance autoionization were observed for low v[sup +] ([lt]10) PFI-PE bands of CO[sup +](X hthinsp;[sup 2][Sigma][sup +]), where the density of interloper Rydberg states converging to higher ionic levels is high as manifested in the photoion spectrum. The observation of a long vibrational progression in the Franck[endash]Condon gap region, where strong autoionization states are absent, is consistent with the suggestion that high-[ital n] Rydberg states converging to highly excited vibrational levels of CO[sup +](X hthinsp;[sup 2][Sigma][sup +]) are partially populated via direct excitation to a repulsive neutral state. The relatively minor band intensity variation observed for high v[sup +] PFI-PE bands is also in accord with the direct excitation model. Since [Delta]N=0, [plus minus]1, [plus minus]2, and [plus minus]3 rotational branches are observed in the PFI-PE spectra, we conclude that the ejected photoelectrons are restricted to angular momentum continuum states l=0[endash]4. [copyright] [ital 1999 American Institute of Physics.]

• OSTI ID: 5903350
• Journal Information: Journal of Chemical Physics, Vol. 111:19; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
CARBON COMPOUNDS
CARBON MONOXIDE
CATIONS
EXCITED STATES
IONIZATION POTENTIAL
MOLECULAR IONS
MOLECULAR STRUCTURE
PHOTOELECTRON SPECTROSCOPY
ROTATIONAL STATES
RYDBERG STATES
VIBRATIONAL STATES
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLES
ELECTRON SPECTROSCOPY
ENERGY LEVELS
IONS
OXIDES
OXYGEN COMPOUNDS
SPECTROSCOPY
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)