## Theses and Dissertations

2016

Dissertation

#### Degree

Doctor of Philosophy

#### Department

Physics

Huennekens, John

This dissertation discusses investigations of vibrationally and rotationally inelastic collisions of NaK with argon, helium and potassium as collision partners. We have investigated collisions of NaK molecules in the $2(A)^{1}\Sigma^{+}$\, state with argon and helium collision partners in a laser-induced fluorescence (LIF) experiment. The pump laser prepares the molecules in particular ro-vibrational (\textit{v}, \textit{J}) levels in the $2(A)^{1}\Sigma^{+}$\, state. These excited molecules then emit fluorescence as they make transitions back to the ground [$2(X)^{1}\Sigma^{+}$\,] state, and this fluorescence is collected by a Bomem Fourier-transform spectrometer. Weak collisional satellite lines appear flanking strong, direct lines in the recorded spectra. These satellite lines are due to collisions of the NaK molecule in the $2(A)^{1}\Sigma^{+}$\, state with noble gas and alkali atom perturbers, which carry population to nearby rotational levels [(\textit{v}, \textit{J})$\rightarrow$ (\textit{v}, $J + \Delta$\textit{J})] or to various rotational levels of nearby vibrational levels, [(\textit{v}, \textit{J})$\rightarrow$ ($v + \Delta$\textit{v}, $J + \Delta$\textit{J})]. Ratios of the intensity of each collisional line to the intensity of the direct line then yields information pertaining to the transfer of population in the collision. Our results show a propensity for $\Delta$\textit{J} = even collisions of NaK with noble gas atoms, which is slightly more pronounced for collisions with helium than with argon. Such a $\Delta$\textit{J} = even propensity was not observed in the vibrationally inelastic collisions. Although it would be desirable to operate in the single collision regime, practical considerations make that difficult to achieve. Therefore, we have developed a method to estimate the effects of multiple collisions on our measured rate coefficients and have obtained approximate corrected values.