The OBrO C(2A2)←X(2B1) absorption spectrum

Abstract

The highly structured visible absorption spectrum of the bromine dioxide radical, OBrO, has been observed in the 15 500-26 000 cm Ϫ1 region. The spectrum is dominated by a long progression in the Br-O symmetric stretching motion (1 Ј) and a series of short progressions built on the bending mode (2 Ј); there are no features associated with the excitation of the antisymmetric stretching mode (3 Ј). The spectrum also contains numerous transitions originating from the ͑0,1,0͒ and ͑1,0,0͒ vibrational levels of the electronic ground state, X(2 B 1). A simultaneous fit to all of the observed vibronic features yielded the frequencies 1 Љϭ799.4 cm Ϫ1 , 2 Љϭ317.5 cm Ϫ1 , 1 Јϭ641.5 cm Ϫ1 , 2 Јϭ210.7 cm Ϫ1 , and a band origin T 0 ϭ15 863 cm Ϫ1. Franck-Condon simulations combined with ab initio calculations of the four lowest OBrO doublet electronic states identify the spectrum as arising from the C(2 A 2)←X(2 B 1) electronic transition.

Photoelectron spectroscopy of higher bromine and iodine oxide anions: Electron affinities and electronic structures of BrO2,3 and IO2–4 radicals

“…1-5 represent transitions from the ground state of the anion (closed-shell) to • are distributed among 26 MOs with the following configuration in the ground state: X 2 B 1 : core (14a 1 ) 2 (2b 2 ) 2 (3a 2 ) 2 (7b 1 ) 1 . 31 The microwave spectrum was analyzed to yield a bent molecule with Br-O bond length of 1.649 Å and O-Br-O bond angle of 114.44 • . 81 The extra electron for the BrO 2 − anion is expected to reside on the singly occupied MO, 7b 1 , to form a closed-shell ground state ( 1 A 1 ).…”

“…The first spectroscopic study (visible absorption) of gas phase BrO 2 was reported by Rattigan et al 25 Since then, a numbers of studies have been devoted to investigate the properties of BrO 2 experimentally employing a variety of techniques, [23][24][25][26][27][28][29] including: rotational spectroscopy, 26 visible absorption in solid matrices, 27, 28 photoionization, 19,29 and high-resolution ultraviolet/visable (UV/Vis) absorption spectroscopy. 30,31 The highly structured visible absorption spectrum of bromine dioxide radical, OBrO, observed in the 15 500-26 000 cm −1 region by Miller et al, 31 was augmented by Franck-Condon simulations and high-level ab initio calculations, and concluded due to the dipole-allowed C( 2 A 2 ) ← X( 2 B 1 ) electronic transition. Several theoretical investigations have been conducted to study the molecular structure, vibrational spectra, and energetics of BrO 2 .…”

“…39 Considering the significance of BrO 2 photodissociation in stratospheric ozone chemistry, it is highly desirable to experimentally study the low-lying excited states and compare them directly with the theoretical predictions. 31,38 Despite the fact that its anion (BrO 3 − ) is commonly found in solutions and solids, [40][41][42][43][44] understanding of the BrO 3 radical is particularly limited. 21 Except for the detection of the BrO 3 radical by photolysis of BrO 3 − aqueous solution 43 or radiation of solid crystals at cryogenic temperatures, 44 there is no other experimental report on this radical.…”

“…Several theoretical investigations have been conducted to study the molecular structure, vibrational spectra, and energetics of BrO 2 . 32-36 Inspired by wellresolved UV/Vis absorption spectra, 25,30,31 high-level ab initio calculations on the ground, as well as the low-lying excited states, have been reported. 31,37,38 Despite these impressive progresses, the low-lying excited states of A( 2 B 2 ) and B( 2 A 1 ) predicted to be in the proximity of C( 2 A 2 ) (Ref.…”

“…32-36 Inspired by wellresolved UV/Vis absorption spectra, 25,30,31 high-level ab initio calculations on the ground, as well as the low-lying excited states, have been reported. 31,37,38 Despite these impressive progresses, the low-lying excited states of A( 2 B 2 ) and B( 2 A 1 ) predicted to be in the proximity of C( 2 A 2 ) (Ref. 38) have not yet been probed experimentally due to extremely small dipole transitions from the ground X( 2 B 1 ) state.…”