Oscillator Strengths and Photodissociation Cross Sections in the X-->A and X-->B' Band Systems in MgH

Accurate theoretical calculations are reported on three low-lying electronic states of MgH. Oscillator strengths, computed for vibrational bands of the X 2 + A 211 and B' 2 + transitions, are estimated to be accurate to within 20% with the X A foo = 0.161. The experi- mental value for the dissociation energy of MgH (D0 = 1.27 + 0.03 eV) is confirmed, and oscillator strengths of the vibration-rotation transitions ( v = 1, 2, and 3) in the ground electronic state are given. In transitions from the ground-state vibrational level, approximately 25% of the X B' oscillator strength lies in the nuclear continuum of the B' state. This X B' photodissociation cross section has been calculated as a function of photon energy. The formation of MgH in the interstellar medium is discussed briefly, and the unshielded interstellar photodissociation rate through the B' state is found to be 6.2 x 10-12 1 Subject headings: interstellar: molecules - molecular processes - transition probabilities