New developments in matrix isolation spectroscopy

In this manuscript we have reviewed some of the more recent matrix isolation studies. Rather than attempting a comprehensive review, we have concentrated on several areas where we either believe the most significant advances were made or which lie in the direct sphere of interest of our own group. The recent developments show that matrix isolation will remain a useful technique for preliminary characterization of radicals, clusters, ions, and other reactive intermediates. In this respect, laser vaporization has provided a very powerful and versatile tool for generation of these species. The recent studies also show that the problems of deposition of mass-selected ions and species can be surmounted, and this will go a long way toward making identification and assignment of matrix spectra easier, reducing thus possibilities of errors and misassignments. Besides studies of transient species, the recent developments also indicate the shift of emphasis from pure spectroscopy toward trying to understand the details of the guest solvation and of guest-host interactions. Very interesting in this context should be studies in novel and unusual matrices, such as the so-called "quantum hosts", for instance solid isotopes of hydrogen, and in solid or liquid helium. The survey of the literature shows that in spite of the fact that more than 70 years have elapsed since the early experiments of Vegard, and 40 since Pimentel has coined its name, matrix isolation remains a very viable and useful technique.