Knowledge Bank

Using stimulated emission pumping with two laser pulses, we have shown that high vibrational levels of a short-lived radical can be studied, and a large population can be prepared at a single, selected, high vibration-rotation level. The first demonstration was performed on the $\nu 3=3$ level of $a1A1CH2$. The methylene radical was produced by photolysis of the ketene molecule. The pump laser pulse excites the $b\leftarrow a201$ transition and the dump laser stimulates emission through the $a\leftarrow b,231$ transitions. In addition to the determination of molecular constants, the double-resonance technique will enable us to determine whether the singlet-triplet coupling that prevails in the $a\leftarrow b$ transitions originates in the a or b state. The double minima in the bending potential can also be characterized.