Stretch-bender calculations of the Rovibronic energies in the excited, (A)over-tilde(2)A(1), electronic state of NH2 and of the near-resonant high-lying levels of the (X)over-tilde(2)B(1) state

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the rovibronic energies in the region where the vibronic states of the excited (A) over tilde (2)A(1) electronic state of NH2 interact with near-resonant high-lying levels of the (X) over tilde B-2(1) state of NH2. A detailed comparison ha's been made with the experimental measurements which were made of these rovibronic states, the majority of which are due to Ramsay, Vervloet, and their collaborators. We have shown that, as in our study of the vibronic levels of the (X) over tilde B-2(1), state below the barrier to linearity, in order to fit the variation of the effective vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A(SO) must be increased from the earlier value of 50 cm(-1) of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys. 40, 65-94 (1980)) to 61.6 cm(-1). The impact of Fermi resonance, in both the (A) over tilde (2)A(1) and (X) over tilde B-2(1) states, on the observed rovibronic structure has been assessed. The pattern of calculated spin-rovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally. (C) 2002 Elsevier Science.