The four potential energy surfaces (PESs) associated, respectively to (1)A', (3)A', (1)A '' and (3)A '' states correlating to the interacting CH(X2 Pi) + Hd(S-2) system, were determined using the aug-cc-pVQZ basis set, and multireference internally contracted configuration-interaction (MRCI) calculation method including the Davidson correction. The CH bond length was fixed at the equilibrium value of the X-2 Pi ground state. The PES of the A' state considerably differs from that of the A '' state. The ab initio calculated interaction energies of the A' and A '' PESs for each spin multiplicity were fitted analytically on the basis of Legendre polynomials. (C) 2008 Elsevier B.V. All rights reserved.