The population distributions of the rotational quantum states of the @ascent MgH(u" =0 and 1) produced in the reaction of Mg(3s3p P& ) with H2 are bimoda1. With the use of the surprisal method, the two components are separated. The minor low-N component of the distribution in the u"=0 state is found to be larger than that in the v" = 1 state, whereas, the major high-E component of the distribution in the v"=0 state becomes roughly equivalent to that in the v"=1 state. The two parallel low-N and high-N processes are expected to correspond to two distinct types of reaction dynamics. One (minor) type produces MgH in lower rotational levels and preferentially v"=0, and the other (major) type produces MgH in higher rotational levels with comparable v" =0 and v" =1 populations. Possible dynamical models are discussed. PACS number(s): 82.30.b, 34.50.s, 35.20.i

By use of Fourier transform near-infrared (NIR) absorption spectroscopy and the aid of a kinetic model, we have investigated the conversion of quadricyclane to norbornadiene catalyzed by anhydrous CuSO 4 and SnCl 2 in chloroform. The reaction mixture is not agitated so as to avoid the effect of sample heterogeneity. The NIR absorption spectra are acquired, at a position ∼2 mm above the catalyst surface, at 30-s intervals during 4 h. The concentrations of quadricyclane and norbornadiene are determined with the analysis of partial least squares. The isomerization of quadricyclane, as numerically solved from the model, is expected to describe its behavior more accurately in the catalytic system than that obtained previously. In addition to the isomerization rate, the kinetic model takes into account the contribution of diffusion. The diffusion coefficients of quadricyclane can be determined to be 3.8 × 10 -5 cm 2 s -1 in chloroform and 1.14 × 10 -5 and 2.85 × 10 -6 cm 2 s -1 inside the CuSO 4 and SnCl 2 stacks, respectively. Diffusion is slowed inside the solid stacks, and thus the molecular mechanism cannot be suitable for this system. Given the diffusion coefficients, the pseudofirst-order depletion rate constants are evaluated to be (3.7 ( 0.1) × 10 -3 and (3.8 ( 0.1) × 10 -3 s -1 for CuSO 4 and SnCl 2 , respectively. The corresponding second-order rate constants are determined to be (1.3 ( 0.2) × 10 -5 and (2.0 ( 0.1) × 10 -6 s -1 A -1 by considering the density and the size of the catalyst particles; A denotes the total catalyst surface area per unit effective volume of solvent. The rate constant with the CuSO 4 catalyst is consistent with others obtained in a continuously stirred mixture. In the surface-mediated reaction, the catalytic isomerization is subject to one-site coordination (1:1 complex) between the reactant and the catalyst. Nevertheless, a two-site coordinated reaction cannot be excluded unless the interstitial size dependence of the depletion rate is known.

By using a step-scan Fourier transform spectrometer, we have studied collisionally-induced rotational energy transfer (RET) of the CH A(2Δ) (N⩽16,v=0) and B(2Σ−) (N⩽16,v=0) states. The collision partners used for the B state are He, Ar, N2, CO, N2O, and CHBr3, while He and Ar are for the A state. The time-resolved spectra obtained in the nanosecond regime may yield the RET information straightforward under a single pressure of the collider. The resultant RET rate constants for both states range from 10−12 to 10−10 cm3 molecule−1 s−1, comparable to the gas kinetic. The trend follows the order of He∼Ar<N2∼CO<N2O<CHBr3 for the B state, and He<Ar for the A state. For the B state, the findings of multi-quantum changing collisions up to ΔN=±3 and markedly large rate constants imply that the RET collisions are dominated by long-range attractive force. The collision complexes possibly formed between the CH(B) and the colliders are long-lived enough to allow for effective removal of the rotational energy more than a quantum level in a single collision. In contrast, a single quantum change in the RET collision found in the A state suggests dominance of a repulsive interaction between the colliding species, which has been verified previously in the measurements of temperature dependence of the electronic quenching.