A study of the BrO and BrO2 radicals with vacuum ultraviolet photoelectronspectroscopy

The BrO radical, prepared by the Br+O-3 reaction, has been investigated by ultraviolet photoelectron spectroscopy. Two vibrationally resolved bands we re observed corresponding to the ionizations BrO+(X (3)Sigma(-))<-- BrO(X ( 2)Pi) and BrO+(a (1)Delta)<-- BrO(X (2)Pi). These assignments are supported by the results of complete active space self-consistent field/multireferen ce configuration interaction (CASSCF/MRCI) calculations performed as part o f this work. The adiabatic ionization energies of these bands were measured as (10.46 +/- 0.02) and (11.21 +/- 0.02)eV, respectively. Measurement of t he vibrational separations in these bands led to estimates of the vibration al constants in the ionic states of (840 +/- 30) cm(-1) and (880 +/- 30) cm (-1), and Franck-Condon simulations of the vibrational envelopes gave value s of the ionic state bond lengths of (1.635 +/- 0.005) and (1.641 +/- 0.005 ) Angstrom for the X (3)Sigma(-) and a (1)Delta states of BrO+, respectivel y. The O+Br-2 reaction was found to give a band at (10.26 +/- 0.02) eV asso ciated with a reaction product. Comparison of the results obtained for the Br+O-3 reaction showed that it could not be assigned to ionization of BrO. Calculations of the first adiabatic ionization energies and Franck-Condon s imulations of the vibrational envelopes of the first photoelectron bands of BrO2 and Br2O and their isomers demonstrated that this band corresponds to the first ionization of OBrO, the BrO2+(X (1)A(1))<-- BrO2(X B-2(1)) ioniz ation. Franck-Condon simulations were performed with the experimental geome try of BrO2(X B-2(1)) but with different cationic state geometries. The sim ulated envelope which most closely matched the experimental envelope gave g eometrical parameters of r(e)=1.6135 Angstrom and angle OBrO=117.5 degrees for the ionic state. (C) 2000 American Institute of Physics. [S0021-9606(00 )00214-2].