Knowledge Bank

The C-H stretch overtone absorptions of ($\Delta \upsilon =5$) of CH$4$, CH$3$D, CH$2$D$2$, and CHD$3$ have been obtained using the phase shift cavity ring down technique. A low temperature cell was designed and adapted to the CRD experiment to measure absorption bands at any temperature between 10 K and 298 K. The spectra were obtained at room temperature and at 110 K. The partially resolved rotational spectrum of CHD$3$ that included the transitions 5$\nu 1$ and 4$\nu 1+2\nu 5$ was obtained and compared with the calculated spectrum. The unresolved vibrational bands around the $\Delta \upsilon =5$ region of CH$2$D$2$, CH$3$D, and CH$4$ were also obtained at several temperatures between 100K and 298 K. The integrated absorption was calculated as a function of the density of the gas samples and used to obtain the cross section and the oscillator strength of the transition for each molecule.