High-resolution pulsed field ionization photoelectron-photoion coincidence spectroscopy using synchrotron radiation
- Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
- Freie Universitaet Berlin, Institut fuer Physikalische und Theoretische Chemie, Takustrasse 3, D-14195 Berlin (Germany)
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290 (United States)
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)
We have developed a sensitive and generally applicable scheme for performing pulsed field ionization (PFI) photoelectron (PFI-PE)-photoion coincidence (PFI-PEPICO) spectroscopy using two-bunch and multibunch synchrotron radiation at the Advanced Light Source. We show that this technique provides an ion internal state (or energy) selection limited only by the PFI-PE measurement. Employing a shaped pulse for PFI and ion extraction, a resolution of 0.6 meV [full width at half maximum (FWHM)] is observed in the PFI-PEPICO bands for Ar{sup +}({sup 2}P{sub 3/2,1/2}). As demonstrated in the PFI-PEPICO study of the process, O{sub 2}+h{nu}{r_arrow}O{sub 2}{sup +}(b&hthinsp;{sup 4}{Sigma}{sub g}{sup {minus}},&hthinsp;v{sup +}=4,&hthinsp;N{sup +})+e{sup {minus}}{r_arrow}O{sup +}({sup 4}S)+O({sup 3}P)+e{sup {minus}}, the dissociation of O{sub 2}{sup +}(b&hthinsp;{sup 4}{Sigma}{sub g}{sup {minus}},&hthinsp;v{sup +}=4) in specific rotational N{sup +} levels can be examined. The simulation of the experimental breakdown diagram for this reaction supports the conclusion that the threshold for the formation of O{sup +}({sup 4}S)+O({sup 3}P) from O{sub 2}{sup +}(b&hthinsp;{sup 4}{Sigma}{sub g}{sup {minus}},&hthinsp;v{sup +}=4) lies at N{sup +}=9. We have also recorded the PFI-PEPICO time-of-flight (TOF) spectra of O{sup +} formed in the dissociation of O{sub 2}{sup +}(b&hthinsp;{sup 4}{Sigma}{sub g}{sup {minus}},&hthinsp;v{sup +}=4{endash}7). The simulation of these O{sup +} TOF spectra indicates that the PFI-PEPICO method is applicable for the determination of kinetic energy releases. Previous PFI-PE studies on O{sub 2} suggest that a high-{ital n} O{sub 2} Rydberg state [O{sub 2}{sup {asterisk}}(n)] with a dissociative ion core undergoes prompt dissociation to yield a high-n{sup {prime}} O-atom Rydberg state [O{sup {asterisk}}(n{sup {prime}})] [Evans {ital et al.}, J. Chem. Phys. {bold 110}, 315 (1999)]. The subsequent PFI of O{sup {asterisk}}(n{sup {prime}}) accounts for the formation of a PFI-PE and O{sup +}. Since the PFI-PE intensities for O{sup +} and O{sub 2}{sup +} depend on the lifetimes of O{sup {asterisk}}(n{sup {prime}}) and O{sub 2}{sup {asterisk}}(n), respectively, the PFI-PE intensity enhancement observed for rotational transitions to O{sub 2}{sup +}(b&hthinsp;{sup 4}{Sigma}{sub g}{sup {minus}},&hthinsp;v{sup +}=4,&hthinsp;N{sup +}{ge}9) can be attributed to the longer lifetimes for O{sup {asterisk}}(n{sup {prime}}) than those for O{sub 2}{sup {asterisk}}(n). The PFI-PEPICO study of the dissociation of CH{sub 3}{sup +} from CH{sub 4} also reveals the lifetime effects and dc field effects on the observed intensities for CH{sub 3}{sup +} and CH{sub 4}{sup +}. The high resolution for PFI-PEPICO measurements, along with the ability to distinguish the CH{sub 3}{sup +} fragments due to the supersonically cooled CH{sub 4} beam from those formed by the thermal CH{sub 4} sample, has allowed the determination of a highly accurate dissociation threshold for CH{sub 3}{sup +} from CH{sub 4}. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 692521
- Journal Information:
- Review of Scientific Instruments, Vol. 70, Issue 10; Other Information: PBD: Oct 1999
- Country of Publication:
- United States
- Language:
- English
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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
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