Quasiclassical trajectory calculations on the chemical reactions Li + XF(v, J = 0)--* LiF + X (X = Mu, IH, 3H, l~ at selected initial atom-diatom orientations, v = 0, 1 and 2 and 15kcalmol-1 of collision energy have been carried out. A potential-induced rotation of the target molecule, favoured by the great angular forces of the system, is, as a rule, necessary for the reactive success of the collision if v = 0 or 1, but not if v = 2. The ease or difficulty of rotation according to whether the molecule is light (MuF or tHF) or heavy (3HF or I~ explains most of the observed orientational dependence of reactivity.

Chlorine B al-I(0+) state lifetimes have been measured by laser-induced fluorescence in several predissociated (v'= 14-19,21) and non-predissociated (v'= 5-12) levels. Trial and error Franck-Condon calculations have been performed to check the nature and position of the predissociating state. The results have been used to give a value of Re for the A aIl(lu) state responsible for predissociation, R 2.48 + 0.01 A. The obtained data show that interference effects due to crossing between B and A states modify the lifetimes of the B state appreciably. The inadequacy of the low-lying vibrational levels region, i.e. v' < 8, to measure the radiative lifetime of the B state (re(B)) is shown. Previous values for re(B) can therefore be affected by considerable errors.

Weakly bound complexes of phenol (Ph) and fluoromethane (CH3F) 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, S0, and first electronic, S1, states, as well as in the ion ground state, I0, yielding the following results: D0(S0)=1540±50 cm−1, D0(S1)=1713±50 cm−1, and D0(I0)=3932±50 cm−1, respectively. In a complementary study, calculations on the complex geometries and binding energies were conducted at the B3LYP/6-31+G* and the MP2/6-31+G* levels. It has been shown that the binding energies computed at the MP2/6-31+G* level are in excellent agreement with the experimental values, whilst those calculated at the B3LYP/6-31+G* level underestimate them by nearly 30%, probably due to the poor description of the dispersion forces.

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