The ultraviolet photodissociation of jet-cooled ClO and BrO radicals

Abstract

Articles you may be interested inPhotodissociation of the BrO radical using velocity map ion imaging: Excited state dynamics and accurate D 0 0 ( Br O ) evaluation Resonance enhanced multiphoton ionization/time-of-flight measurements of the velocity and internal energy content of thermal and photochemical methyl radical sources Rev.The photodissociation dynamics of jet-cooled ClO and BrO radicals have been studied using resonance-enhanced multiphoton ionization with time-of-flight mass spectrometry. Four asymptotic electronic channels are energetically allowed for ClO photodissociation at 235 nm, although the dominant products observed at 235 nm are Cl( 2 P 3/2 ) and O( 1 D 2 ). Polarization-dependent time-of-flight profiles indicate that this channel has an anisotropy parameter of ␤ϭ1.2Ϯ0.2. Evidence for O( 3 P J ) products was detected in coincidence with Cl( 2 P 1/2 ) fragments, and we estimate that this channel constitutes Ͻ3% at this wavelength. In the photodissociation of BrO at 355 nm we observe two asymptotic electronic state channels, Br( 2 P 3/2 )ϩO( 3 P 2 ) and Br( 2 P 1/2 ) ϩO( 3 P 2 ) in a 0.75:0.25 ratio. Both channels have an anisotropy parameter of ␤ϭ1.5Ϯ0.1. Based on the measured asymptotic velocities of both channels, we have directly determined the Br-O bond dissociation energy to be 55.8Ϯ1.0 kcal/mol, providing a heat of formation for the BrO radical at 298 K of 29.7Ϯ1.0 kcal/mol in good agreement with previous spectroscopic determinations.

Inhibition of hydrogen oxidation by HBr and Br2

“…For BrO, the ATcT TN contains a number of experimental determinations that are relevant to defining its D 0 [65][66][67][68][69][70][71]. These are complemented by the results of several high-level electronic structure computations [72][73][74][75][76][77][78], which, if and when possible, were recast as congeneric reactions, adding within the TN relevant interdependences between various haloxyl radicals and/or their ion counterparts (halosyls and hypohalites).…”

The UV photodissociation dynamics of ClO radical using velocity map ion imaging

“…25 The final images were obtained by repeatedly scanning Doppler profiles of Cl͑ 2 P 3/2 ͒ /Cl͑ 2 P 1/2 ͒ to achieve homogeneous detection efficiency. Since cylindrical symmetry with respect to the electric field was maintained throughout the experiments, the two-dimensional projections were reconstructed to the original three-dimensional ion spheres by applying the basis-set expansion ͑BASEX͒ method developed by Drinbinski et al 26 In our previous work on ClO photodissociation the radicals were generated using a pulsed electric discharge 27,28 similar to the approach of Cooper et al 18,29 We find that an intense molecular beam of ClO radicals can be generated using the flash pyrolysis of a Cl 2 O / He mixture. The active region of the pyrolysis source consists of a 3 cm alumina tube wrapped with nickel-chrome alloy wire which is resistively heated to approximately 800 K. 30 Figure 1 demonstrates the production of ClO radicals using the pyrolytic source.…”

“…Zou et al studied the photodissociation of ClO near 235 nm using 2 + 1 resonance-enhanced multiphoton ionization ͑REMPI͒ with time-of-flight mass spectrometry ͑TOFMS͒. 18 The authors reported that channel ͑3͒ was the dominant channel with anisotropy parameter of 1.2± 0.2, suggesting that the photodissociation dynamics of ClO at 230-250 nm is not strongly wavelength dependent. Schmidt et al investigated photodissociation of ClO over the wavelength range of 205-270 nm employing 2 + 1 REMPI detection of O͑ 1 D 2 ͒.…”

An ab initio investigation on the ground electronic state of chlorine monoxide and its singly charged cation and anion

“…Thereafter, a variety of experimental techniques have been performed to study ClO, including methods of flash photolysis [8][9][10] spectroscopy [11], microwave spectroscopy [12][13][14][15], ultraviolet spectroscopy [16,17], matrix isolation [18], laser magnetic resonance spectroscopy [19], infrared spectroscopy [20,21], multiphoton ionization spectroscopy [22,23], laser-induced fluorescence spectroscopy [24], resonance-enhanced multiphoton ionization [25][26][27] and velocity-map ion-imaging [28][29][30]. Efforts have also been made on the accompanying theoretical analyses [31][32][33][34][35][36].…”