Knowledge Bank

A laser-induced fluorescence spectrum (355-450 nm) has been recorded for the $A2\Pi -X2\Pi$ and $B2\Sigma -\ast X2\Pi$ band systems of the radical NCS rotationally cooled in a supersonic free jet expansion. A detailed analysis has been carried out for the A-X system. The linear radical NCS is of interest because of the Renner-Teller interaction in both the A and X states and because of the large spin-orbit coupling constant ($A=323.4cm-1$) in the ground electronic state relative to the Renner-Teller splitting $\epsilon \omega 2=69cm-1)$. The detailed information available from this study for all three vibrational modes provides a good test of the ability of the current Renner-Teller models to describe the spectrum of such a species. A detailed vibronic analysis has been carried out for the A and X electronic states for the two stretching modes excited by up to three quanta and for excited bending levels. Rotational analyses were conducted for the stronger bands involving each of the three vibrational modes. Results of these analyses will be presented at the meeting. Problems with the use of the Renner-Teller models to fit the excited bending levels will be discussed. This research was carried out at Brookhaven National Laboratory under Contract No. DE-ACO2-76CH00016 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.