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Molecular beam photoionization study of SO/sub 2/ and (SO/sub 2/)/sub 2/

Journal Article · · J. Chem. Phys.; (United States)
OSTI ID:6315583
Photoionization efficiency (PIE) data for SO/sub 2//sup +/ have been obtained with a wavelength resolution of 0.14 A (FWHM) in the region 625--1005 A using the molecular beam method. The ionization energy (IE) of SO/sub 2/ was determined to be 12.348 +- 0.002 eV (1004.08 +- 0.20 A). Similar to the observation in the PIE curve for O/sub 3//sup +/, the spacing for steplike structure observed near the threshold was found to be irregular. Weak structures which arise by autoionization from different vibrational states of Rydberg levels were also resolved in this region. The analysis gives average vibrational spacing of 386, 428, 716, 745, 911, 938, and 956 cm/sup -1/ for these Rydberg states. The appearance energy (AE) for the photodissociative ionization processes SO/sub 2/+h..nu -->..SO/sup +/+O+e/sup -/ and S/sup +/+O/sub 2/+e/sup -/ were measured to be 15.953 +- 0.010 eV (777.2 +- 0.5 A) and 16.228 +- 0.030 eV (764 +- 1.5 A), respectively. Using the AE for the formation of SO/sup +/ from SO/sub 2/, and the heats of formation of SO/sub 2/, SO, and O, the IE of SO is deduced to be 10.28 +- 0.02 eV. This value is in excellent agreement with that reported previously by Dyke et al. From the observed IE (11.72 +- 0.03 eV) of (SO/sub 2/)/sub 2/, the IE of SO/sub 2/, and the estimated binding energy (0.03 eV) of (SO/sub 2/)/sub 2/, the bond dissociation energy of SO/sub 2//sup +/ x SO/sub 2/ is found to be 0.66 +- 0.04 eV. Using the measured AE (15.38 +- 0.06 eV) for S/sub 2/O/sub 3/2= production from (SO/sub 2/)/sub 2/, a lower bound for the binding energy of SO/sup +/ x SO/sub 2/ was calculated to be 0.60 eV.
Research Organization:
Ames Laboratory, Department of Chemistry, Iowa State University, Ames, Iowa 50011
OSTI ID:
6315583
Journal Information:
J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 75:4; ISSN JCPSA
Country of Publication:
United States
Language:
English