Rotationally resolved pulsed field ionization photoelectron bands of O[sub 2][sup +](X [sup 2][Pi][sub 1/2,3/2g],v[sup +]=0[endash]38) in the energy range of 12. 05[endash]18. 15 eV

Journal Article · Sun Aug 01 04:00:00 EDT 1999 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.479459· OSTI ID:6270751

Song, Y; Evans, M; Ng, C Y ^[1]; Hsu, C; Jarvis, G K ^[2]

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1. Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)
2. Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

We have obtained rotationally resolved pulsed field ionization photoelectron (PFI-PE) spectra for O[sub 2] in the energy range of 12.05[endash]18.15 eV, covering ionization transitions O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], hthinsp;v[sup +]=0[endash]38,J[sup +])[l arrow]O[sub 2](X hthinsp;[sup 3][Sigma][sub g][sup [minus]], hthinsp;v[sup +]=0,N[sup [double prime]]). While the PFI-PE bands for O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], v[sup +]=3[endash]5, 9, 11, 12, 22, and 25[endash]38) reported here are the first rotational-resolved photoelectron measurements, the PFI-PE bands for O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], hthinsp;v[sup +]=25[endash]38) represent the first rotationally resolved spectroscopic data for these states. The simulation of spectra obtained at rotational temperatures of [approx]20 and 220 K allows the unambiguous identification of O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], hthinsp;v[sup +][ge]21) PFI-PE bands, the majority of which overlap with prominent PFI-PE bands for O[sub 2][sup +](A hthinsp;[sup 2][Pi][sub u], hthinsp;v[sup +]=0[endash]12) and O[sub 2][sup +](a hthinsp;[sup 4][Pi][sub u], hthinsp;v[sup +]=0[endash]18). Combined with spectroscopic data obtained in the previous emission study and the present PFI-PE experiment, we have obtained accurate Dunham-type expansion coefficients for ionization energies, vibrational constants, rotational constants, and spin[endash]orbit splitting constants covering the O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], hthinsp;v[sup +]=0[endash]38) states. Significant local intensity enhancements due to near-resonant autoionization were observed in PFI-PE bands for O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g], hthinsp;v[sup +]=0[endash]14). The energy region of these states is known to manifest a high density of very strong autoionizing low-[ital n]-Rydberg states. The observation of a long PFI-PE vibrational progression with a relatively smooth band intensity profile is also in accord with the direct excitation model for the production of highly vibrationally excited O[sub 2][sup +](X hthinsp;[sup 2][Pi][sub 1/2,3/2g]) states in the Franck[endash]Condon gap region. Since this experiment was carried out under relatively high rotational temperatures for O[sub 2], the PFI-PE data reveal higher rotational transitions and numerous local intensity enhancements, which were not observed in previous vacuum ultraviolet laser studies using a cold O[sub 2] molecular beam. The rotational branches found here indicate that photoelectrons are formed predominantly in continuum states with orbital angular momenta l=1,3, and 5. [copyright] [ital 1999 American Institute of Physics.]

• OSTI ID: 6270751
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Vol. 111:5; 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
CATIONS
CHARGED PARTICLES
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EV RANGE
EV RANGE 10-100
EXCITED STATES
FRANCK-CONDON PRINCIPLE
IONIZATION
IONS
MOLECULAR IONS
NONMETALS
OXYGEN
OXYGEN IONS
PHOTOELECTRON SPECTROSCOPY
ROTATIONAL STATES
SPECTROSCOPY
VIBRATIONAL STATES