Knowledge Bank

Methylene ($CH2$) has been the subject of numerous studies since Herzberg and $Johns1$ first analyzed the $b~\leftarrow a~$ electronic spectrum in 1966. The electronic spectrum of $CH2$ is complicated by singlet-triplet interactions between the $a~,b~$, and $X~3B1$ states, the Renner-Teller Effect between the $b~$ and $a~$ states, which correlate with a degenerate $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta g$ state at the linear configuration, and spin-orbit coupling. Recently, Green et $al.2$ reported a theoretical investigation of the $CH2b~\leftarrow a~$ electronic spectrum. In this study, they predicted the positions of many more vibronic bands than were observed by Herzberg and $Johns.1$ Although the visible spectrum of $CH2$ has been quire extensively studied, there are very few experiments in near-IR region due to less efficient dye laser operation at longer wavelengths. We have constructed a Ti:sapphire laser based transient absorption spectrometer and have measured the $CH2b~\leftarrow a~$ electronic spectrum between 11400 and $12500cm-1$ at Doppler limited resolution. Our spectrum has indeed shown more lines than the previous $report.1$ Furthermore, reassignments of several previously $observed1$ bands suggested by Green et $al.2$ have bee confirmed. The analysis is still in progress. The new experimental data nd current state of the analysis will be presented. Acknowledgment: This work w carried out under Contract No. DE-AC02-76CH00016 with the U. S. Department of Energy and supported by its Office of Basic Energy Science, Division of Chemical Sciences.