A laser spectroscopic study of the excited states and dynamics of aluminum hydride, hydrogen chloride, nitrogen dioxide, ethene and iodomethane
Abstract
The production of radical transients AlH in a filament-source pulsed free-jet expansion is investigated. In this source, hydrogen gas from a pulsed valve passes over hot tungsten filament wrapped by a layer of aluminum wire to produce AlH or AlH$\sb2.$ The source has been characterized by LIF and ionization-detected one-photon absorption with time-of-flight mass resolution. LIF measurement focus on the well-known A-X transition of AlH. Higher energy ionization-detected absorption spectra resolve the $\rm C\sp1\Sigma\sp+$-$\rm X\sp1\Sigma\sp+$ transition in AlH and AlD, and for the first time the forbidden transition, $\rm b\sp3\Sigma\sp-$-$\rm X\sp1\Sigma\sp+,$ in AlH. The angular momentum selection rules for NO$\sb2$ photodissociation have been derived by applying appropriate coupling schemes. The obtained selection rules of $\Delta$J and parity propensity are applied to explain the angular momentum correlation in the earlier experimental results of NO$\sb2$ photodissociation. The ungerade Rydberg states of acetylene in the energy range from 79,400-85,000 cm$\sp{-1}$ have been investigated by (3+1) REMPI spectroscopy. Bending vibrational transitions induced by Renner-Teller coupling have been discovered and analysed. Based on intensities observed in our spectrum, we offer a reassignment of this bending level structure, that suggests an acetylene cation, both isolated and at the core of non-penetrating Rydberg states, in which the trans-bend is of relatively high frequency and strongly coupled by Renner interaction to the cation $\sp2\Pi$ electronic degeneracy. The rotationally resolved spin-orbit autoionization spectrum of HCl has been obtained in double resonance via levels of lowest angular momentum in v = 0 of the 4p$\sigma$ D$\sp1\Pi$ state. A self-consistent assignment is offered of the portion of the spectrum ranging over principal quantum numbers from 13 to 18, and compared to MQDT calculations. The theoretical calculation are in the good agreement with experiment results. The two-photon UV and the one-photon VUV ZEKE spectra of CH$\sb3$I have been obtained. The progression of C-I stretch vibrational mode is appeared in the two-photon ZEKE spectra but absent in one-photon ZEKE spectra which indicate that the coherent wavepacket on the dissociative surface opens Franck-Condon channels for threshold ionization. Under the field-free condition, the strong autoionizing states of the iodine atom converging to $\rm\sp3P\sb1$ IP are resolved in ZEKE spectrum.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Chemistry
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