Knowledge Bank

The $\nu 3$ fundamental vibration rotation band of carbon-13 enriched methane $(13CH4)$ was recorded using a high resolution vacuum infrared grating spectrograph. Forbidden transitions of this band are reported for the first time. Of the nearly 900 transitions identified, 560 are forbidden transitions are 332 of the forbidden transitions have $11\le J\le 16$. Pairs of forbidden-allowed transitions having the same upper state energy levels were used to calculate 550 linearly independent differences between ground state energy levels. From these data, a least-squares method was used to calculate the following ground state structure constants and their standard deviations (in $cm-1$):\begin{eqnarray*}\beta^{O}/hc&=&5.240820\pm0.000056\ \gamma^{O}/hc&=&-(1.0856\pm0.0015)\times 10^{-4}\ \in^{O}/hc&=&-(1.4174\pm0.0034)\times 10^{-6}\ \xi^{O}/hc&=&-(1.73\pm0.37)\times 10^{-11}\end{eqnarray*} The 550 combination differences utilized in the calculation can be reproduced with the stated constants with an overall standard deviation of $0.0155$ $cm-1$.