Knowledge Bank

As part of a comprehensive effort to compile line parameters of methane from 2400--3200 $cm-1$, the P and R branches of the $\nu 2+\nu 3-\nu 2$ band of $CH4$ at $3010cm-1$ have been assigned. This process utilized the analysis of $\nu 2+\nu 3$ at $4544cm-1$ by Hilico et. al. and the $\nu 2$ levels derived from the infrared spectrum by Margolis to predict the positions of the hot band. Experimentally determined lower state energies have been used to confirm assignments, and room temperature line intensities are observed on the order of $10-3$ $cm-2$ $atm-1$ or less. At each J, the strongest hot band P branch lines occur at the highest energy levels of $\nu 2+\nu 3$, While the strongest R branch lines occur at the lowest levels. These data indicate a selection rule of $\Delta E=0$ hand also $\Delta NE=0$ for this hot band.