Knowledge Bank

We report the results of our preliminary investigations into the suitability of condensed phase parahydrogen as a Raman-shifting medium for the generation of tunable infrared radiation for cavity ringdown laser absorption spectroscopy (CR-LAS). We have observed the conversion of $\sim 10$ ns pulses of 532 nm radiation into first-, second-, and third-order vibrational Stokes radiation in bulk liquid and solid parahydrogen after a single 11-cm pass. Surprisingly, we find that liquid-$H2$ yields more efficient conversion than solid-$H2$ with certain focal geometries, and that in the case of the solid, a collimated or loosely focused pump geometry is more efficient than a tight focus. We also will discuss our more recent studies of Raman shifting using the longer $(\sim 100ns)$ pulses of an alexandrite laser.