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

• Published in: The Journal of chemical physics 1999-08, Vol.111:5
• Main Authors: Song, Y., Evans, M., Ng, C.Y., Hsu, C., Jarvis, G.K.
• Format: Article
• Language: English
• Subjects: 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 664200 > Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-); VIBRATIONAL STATES
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.479459

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 c