| Experimental and theoretical work in molecular reaction dynamics seeks to quantitatively describe and (ultimately) control the quantum state-specific behavior of chemical reactions. For the experimentalist, this requires full initial quantum state selection of the reagents. In this dissertation, the photodissociation of CD{dollar}sb3{dollar}I, as system extensively studied both theoretically and experimentally, will be reexamined with energy level and quantum state selectivity. In these experiments the parent molecules were vibrationally cold ({dollar}v = 0{dollar} for all vibrational modes) and individual rotational (J,K,M) states were prepared. This was accomplished via a supersonic molecular beam expansion and the use of the UCLA electrostatic hexapole machine, which has been demonstrated to effectively select and focus high intensity beams of single {dollar}vert JKM{lcub}>{rcub}{dollar} state-selected molecules. Following A-band dissociative excitation, the {dollar}vert{dollar}NK) rotational energy level distribution of the CD{dollar}sb3{dollar} photoproduct was determined using (2 + 1) resonance-enhanced multiphoton ionization (REMPI). Previous models for CD{dollar}sb3{dollar}I A-band photodissociation assumed helicity conservation throughout the process ({dollar}Delta K = 0{dollar}), i.e., no torque is generated about the C-I axis. Although {dollar}Delta K = 0{dollar} scattering appears to be the dominant process, our results show that significant amounts of {dollar}Delta K = {lcub}pm{rcub}3{dollar} scattering also occurred. This lack of helicity conservation is attributed to scattering from regions near the conical intersection between excited state surfaces that correlate asymptotically to the I{dollar}sp*(sp2Psb{lcub}1/2{rcub}{dollar}) and I({dollar}sp2Psb{lcub}3/2{rcub}{dollar}) energy levels of the atomic iodine fragment. Total scattering into all K levels of a given N level of the CD{dollar}sb3{dollar} fragment agrees well with recent quantum calculations. Photofragment Excitation Curves were also measured. In these experiments, the {dollar}vert JKM{lcub}>{rcub}{dollar} state distribution of the parent CD{dollar}sb3{dollar}I molecule scattering into specific {dollar}vert N,K{dollar}) levels of the CD{dollar}sb3{dollar} radical were measured and found to agree with the dominant but not exclusive helicity conservation mechanism for the scattering process. Finally, angular distributions of photofragments from state-selected parent molecules show the failure of semi-classical models to adequately describe true quantum state to quantum state photochemistry. |
