Experimental and theoretical study of the Li+HF (v=1)→LiF+H reaction

Abstract

Laboratory angular distributions (LAB ADs) have been measured for the Li ] HF (v \ 1, j \ 1) reaction in a crossed molecular beam experiment at the collision energies 0.231 eV and 0.416 eV and compared with the results of extensive quasi-classical trajectory (QCT) calculations performed on the most recent ab initio potential energy surface (PES) for this system. The calculations also include the collision energy dependence of the integral and di †erential cross sections in the range 0.025È0.5 eV (2.4È48.2 kJ mol~1). In particular, the total QCT integral reactive cross sections have been found to be in very good agreement with recent quantum mechanical (QM) calculations carried out on the same PES by Lara et al. (J. Chem. Phys., 1998, 109, 9391). In addition, the triple scattering angleÈrecoil velocity di †erential cross section has been calculated in order to simulate the experimental LAB AD. An excellent concordance between both sets of data has been found, indicating that the reaction of Li with HF in v \ 1 can be very well described by QCT calculations on the mentioned PES.

Polarization of molecular angular momentum in the chemical reactions Li + HF and F + HD

“…More ICS experiments have been carried out by Lee et al 53 and by Loesch et al 47,[54][55][56] Theoretically, the steric effect has been analyzed for the case of initially ro-vibrational excited HF molecules, HF(v r = 1, j r = 1) using quantum 48 and quasi-classical approaches (QCT). 25,49,56,58 The results obtained were in good agreement with experiment. 8,50,52 Both experiments and calculations have shown that the initial vibrational excitation of HF increases the reactivity 8,[48][49][50]59 enormously, because of the late character of the reaction barrier.…”

“…25,49,56,58 The results obtained were in good agreement with experiment. 8,50,52 Both experiments and calculations have shown that the initial vibrational excitation of HF increases the reactivity 8,[48][49][50]59 enormously, because of the late character of the reaction barrier. This is also the reason why simulations indicate that the reaction cross section depends strongly on the rotational alignment of HF reagents in their ground v r = 0 vibrational state, because collinear collisions favor the excitation of the vibrational stretch needed to overpass the late barrier.…”

“…Among these systems, the reaction Li + HF → LiF + H is a prototype which has already been a subject of several stereodynamic studies. 25,[47][48][49] Loesch and co-workers excited HF from the ground vibrational state to the v r = 1, j r = 1 state using linearly polarized laser within the condition of crossed-beam experiment. 8,[49][50][51][52] By changing the laser beam polarization, the molecular orbital angular momenta j r = 1 were aligned either parallel, or perpendicular to the relative velocity vector k. The integral (ICS) and differential (DCS) cross sections obtained have shown important steric effects, favoring a side attack.…”

“…25,[47][48][49] Loesch and co-workers excited HF from the ground vibrational state to the v r = 1, j r = 1 state using linearly polarized laser within the condition of crossed-beam experiment. 8,[49][50][51][52] By changing the laser beam polarization, the molecular orbital angular momenta j r = 1 were aligned either parallel, or perpendicular to the relative velocity vector k. The integral (ICS) and differential (DCS) cross sections obtained have shown important steric effects, favoring a side attack. More ICS experiments have been carried out by Lee et al 53 and by Loesch et al 47,[54][55][56] Theoretically, the steric effect has been analyzed for the case of initially ro-vibrational excited HF molecules, HF(v r = 1, j r = 1) using quantum 48 and quasi-classical approaches (QCT).…”

Transition state spectroscopy of the excited electronic states of LiHF

“…Aside from the experimental problems related to its study, there are several works on the LiϩHF collisions, [33][34][35][36][37][38] and the LiHF(A,B,BЈ←X) electronic absorption spectrum has recently been measured by Polanyi and co-workers. 26 On the theoretical side, there is an increasing number of ab initio studies to characterize the potential energy surfaces ͑PESs͒ on the ground [39][40][41][42][43] and more recently also on the excited 44,45,42 electronic states, and many theoretical studies to simulate the collision, using quantum 39,40,46 -49 as well as classical 50,37 methods on the ground electronic state. Also some theoretical studies have been devoted to the spectroscopic study of the transition state by infrared excitation on the ground electronic state.…”