True quantum state-to-quantum state chemistry: Experimental determination of the transition dipole matrix.

摘要

The dynamics of photodissociation reactions of 2 different systems were studied in detail. For both systems the initial {dollar}vert JKMrangle{dollar} rotational state was selected using an electrostatic hexapole "filter." Selection of the initial reactant quantum state coupled with state-selective detection of the photoproducts allows determination of the greatest amount of information possible for a chemical reaction. This in turn allows determination of the molecule-specific transition dipole matrix elements (T-matrix) which contains all of the dynamical information for the chemical reaction.; In the first experiment a beam of deuterated methyl iodide, {dollar}rm CDsb3I,{dollar} seeded in xenon (5-10%) was focused by the electrostatic hexapole into the {dollar}vert 111rangle{dollar} rotational state of the vibrationless ground electronic state, {dollar}tilde X sp1Asb1.{dollar} The state-selected molecules were then photodissociated in the A band by a laser at 266 nm. The population and alignment (second and fourth rank spherical moments) of several of the individual rotational states (low total angular momentum, {dollar}Jle 2){dollar} of the methyl photofragment were then measured via (2+1) REMPI via the {dollar}rm 3psp2Asbsp{lcub}2{rcub}{lcub}primeprime{rcub}gets 2psp2Asbsp{lcub}2{rcub}{lcub}primeprime{rcub}{dollar} electronic transition. Quantum state-specific angular distributions of the methyl photofragments were measured via time-of-flight (TOF) spectroscopy. In addition, from these measurements of the detailed cross sections (both integral and differential), elements of the T-matrix were calculated, representing the highest level of detail possible for a photodissociative reaction.; In the second experiment a beam of nitrosyl chloride (NOCl) seeded in argon (10-50%) was state selected by the electrostatic hexapole and then photodissociated in the B band at {dollar}{lcub}sim{rcub}355{dollar} nm. The angular distribution, state population, and rotational alignment of several product nitric oxide (NO) rotational states (high total angular momentum, {dollar}Jge 39.5){dollar} were determined. The product NO rotational distribution was quite hot, with a peak in the distribution much higher than {dollar}J = 30{dollar} with a propensity for {dollar}{lcub}bf J{rcub}{dollar} (total angular momentum) to be oriented perpendicular to the laboratory Z-axis. From measurements of both the angle-integrated alignment moments and the photofragment angular distributions, possible T-matrix amplitudes and phases were estimated.