DIODE-LASER SPECTROSCOPY OF COMPLEX-MOLECULES WITH ENCLOSIVE FLOW COOLING FOR SPECTRAL SIMPLIFICATION

The enclosive flow cooling technique proved to be an efficient tool fo r simplifying molecular spectra. Compared to supersonic jet cooling, i t provides high optical absorption efficiency. In this work, the proto type enclosive flow cooling cell was combined with tunable diode laser spectroscopy (TDLAS). The cell is easy to handle and use. With liquid nitrogen a gas temperature of 115 K was achieved. The fundamental spe ctral cooling effects, namely the reduction of line width and the decr ease of spectral line number density, were investigated on CH4 and CHF 3 and compared with theoretical expectations. Single-line resolution w as improved by a factor of 5. Maximum absorption was enhanced by a fac tor of 2.5. Using the new cooling technique the number of molecules de tectable in trace concentrations by TDLAS may be extended considerably ,especially at temperatures lower than those attainable with liquid ni trogen. Experiments in this direction are planned for the future.