Should bromoform absorb at wavelengths longer than 300 nm ?

A theoretical study of the low-lying singlet and triplet electronic states of CHBr3 is presented. Calculations of excitation energies and oscillator strengths are presented using excited state coupled cluster response methods, as well as the complete active space self-consistent field method with the full Breit–Pauli spin–orbit operator. These calculations predict that for CHBr3 there is only one singlet state, the ÃA2 , that is accessible by wavelengths longer than 234 nm. It is, however, predicted to be very weakly absorbing, but may strongly overlap at shorter wavelengths with a higher B̃E state, which itself is predicted to be strongly absorbing. There is one triplet state, the ãA2 , that lies well below the à A2 state and has a predicted absorption maximum at about 270 nm. The band origin of the ãA2 is predicted to lie around 297 nm, but this C3v symmetry minimum is calculated to be a second-order transition state, ultimately leading to dissociation to HCBr21Br. © 2002 American Institute of Physics. @DOI: 10.1063/1.1502639#