Rotational state selection and orientation of diatomic and asymmetric top molecules via the electric hexapole technique

The hexapole rotational state selection of 2∏ _Ω diatomic and asymmetric top molecules is investigated. Classical molecular trajectory simulations are shown to reproduce experimental focusing spectra in these large classes of molecules. Deviations from linear Stark effects introduce significant effects in the focusing behavior of both the 2∏ and asymmetric rotor species. The laboratory frame distributions of orientations of the state-selected molecules are quantified by quantum mechanical orientational probability distribution functions (opdf's).; Chapter 1 introduces preliminary data for the hexapole focusing of hydroxyl radicals and shows the deviation of the structured focusing curves from the first-order Stark effect. In Chapter 2, the focusing theory is developed for 2∏ diatomics, and the focusing spectra presented in Chapter 1 are analyzed using the theory. The Λ-doublet splitting is found to be the important parameter for simulating the measured focusing spectra. The high field limit opdf's are calculated, and highly anisotropic orientational distributions for the selected states are shown.; Chapter 3 shows the laboratory orientation of 2∏ molecules is tunable via the electric field strength of an orienting field for post-hexapole selected rotational states. A laser induced fluorescence experiment is detailed allowing experimental validation of the theoretical opdf's. Chapter 4 explores the scattering of hexapole selected OD rotational states with various target gases. Elastic scattering cross sections are reported for OD + M (M = He, Ar, H₂O, CO₂, NH₃, and CH₃F).; Hexapole focusing and the subsequent orientation of asymmetric rotors are the subjects of Chapter 5. Matrix treatments are used to calculate the field-free and Stark energies exactly. Perturbation and intermediate Stark effect approximations are compared to the exact matrix method, yielding several general rules useful in analyzing and predicting experimental focusing spectra. The theory needed for the calculation of asymmetric top opdf's is also presented. Source code for calculating asymmetric top zero-field and Stark energies as well as the opdf's appear in Appendix A. Finally in Chapter 6, the methods of Chapter 5 are applied to analyze focusing spectra of plasma generated radical beams where multiple radical species comprising the beam complicate the measured focusing spectra in specific mass spectral channels.