Knowledge Bank

The $\nu 10(E\prime )+\nu 11(E\prime )$ perpendicular band of cyclopropane $C3H6$ in the $1880-1905cm-1$ region has been studied with tunable diode lasers. Spectra were recorded using a double beam system with one path passing through the sample and the other through etcher a Ge etalon or an $N2O$ cell. The $N2O$ lines are spaced roughly $0.8cm-1$ throughout this region and provide a convenient and very precise $(\pm 10-4cm-1)$ method of $calibration1$ Analysis of this band is complicated by the fact that 2B is approximately equal to the Q-branch spacing, so that each Q branch is overlapped by a cluster of $PP$ or $RR$ lines having a common J-K value. Over 360 lines have been assigned. Preliminary results from ground state combination differences yield $B\prime \prime =0.67014\pm 0.00006cm-1$ and $ D^{\prime\prime}_{J}=(6.23 \pm 1.64)\times 10^{-7} cm^{-1}$, in good agreement with the results obtained by McCubbin \emph{et al}. $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ from the $\nu 6$ parallel band. For the excited state we find (in $cm-1$) $2[C\prime (1-\zeta )-B\prime ]=-1.363,B\prime -B\prime \prime =-1.58\times 10-3,C\prime -C\prime \prime =-3.83\times 10-3$. The $\zeta$ value obtained from these constants is $\zeta =1.031$, consistent with the relation $\zeta =\ell 10\zeta 10+\ell 11\zeta 11$ with $\ell 10=\ell 11=-1,\zeta 10=-0.073,$, and $\zeta 11=-0.96$.$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$