Physical aspects of matrix isolation technique: FTIR studies on CO and CO2in O-2 and N-2 matrices

The matrix isolation technique is traditionally used to investigate the pro perties of the matrix-isolated species themselves or to solve some special questions of the theory of defects in solids. We showed here that the optic al spectroscopy of real matrix-isolated molecules can be successfully used to investigate the host crystal qualities, too. We demonstrated the capacit y of modern FTIR spectroscopy to study the properties of cryocrystals such as phase transitions, solubility boundaries, orientational order parameter, etc., by monitoring the behavior of the IR-active molecules, which are pre sent in matrices under investigation as a natural contamination (40 ppb). D ue to the excellent optical quality of our crystal samples, we were able to determine a part of the binary phase diagram CO-O-2 (at CO concentrations less than 1 ppm) as well as to investigate the kinetics of phase transition s. Furthermore, we successfully used the spectroscopy of the matrix-isolate d molecules to proof that the alpha-beta phase transition of the matrix cry stal (O-2) is of first order. (C) 2000 American Institute of Physics. [S106 3-777X(00)01109-9].