Experimental determination of phenol (CH[sub 3]F)[sub 1] complex binding energies in the S[sub 0], S[sub 1], and I[sub 0] states and comparison with ab initio calculations.

Weakly bound complexes of phenol (Ph) and fluoromethane (CH[sub 3]F) formed in a supersonic expansion have been identified by one- and two-color mass-resolved and hole burning spectroscopies. Only one isomer has been observed for the 1:1 complex. Threshold fragmentation has been employed to determine the binding energies of the complex in its ground, S[sub 0], and first electronic, S[sub 1], states, as well as in the ion ground state, I[sub 0], yielding the following results: D[sub 0](S[sub 0])=1540±50 cm[sup -1], D[sub 0](S[sub 1])=1713±50 cm[sup -1], and D[sub 0](I[sub 0])=3932±50 cm[sup -1], respectively. In a complementary study, calculations on the complex geometries and binding energies were conducted at the B3LYP/6-31+G[sup *] and the MP2/6-31+G[sup *] levels. It has been shown that the binding energies computed at the MP2/6-31+G[sup *] level are in excellent agreement with the experimental values, whilst those calculated at the B3LYP/6-31+G[sup *] level underestimate them by nearly 30%, probably due to the poor description of the dispersion forces. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]