We report a new ab initio potential energy surface of the excited ((A) over cap (1)A") state of HCN/ HNC and the transition dipole function to the ground ((X) over cap (1)A') state at the MRCI/aug-cc-pVTZ level of theory. Resonance emission spectra from several low-lying and predissociative vibrational states of the HNC((A) over cap (1)A") isomer are calculated, which show the dominance of the C-N progressions, due apparently to the large difference in the equilibrium C-N bond lengths in the two electronic states. (C) 2008 Elsevier B.V. All rights reserved.