Infared diode laser double-beam spectrometer

Abstract

A complete spectrometer for recording high resolution ir absorption spectra with diode lasers is presented. The optical assembly has been adapted to the characteristics of diode lasers but can be used as well with other laser sources. With a double-beam technique variations in laser power are eliminated. Problems of optical alignment and electronic signal detection are discussed, and representative spectra are presented.

Nonphotochemical hole burning and the nature of amorphous solids

“…Gunthard after irradiation into the band of trans-1,2-difluoroethane in solid argon or krypton using a diode laser (61,62). For an argon matrix deposited at 17K, a hole burned at 6K has a Lorentzian profile of width 0.006 cm~^.…”

“…NPHB was discovered in the course of FLN studies of molecules imbedded in organic glasses (55,57). When NPHB occurs, FLN is usually observed as well (55)(56)(57)(58)(59)(60)(63)(64)(65)(66), and each has been used to probe the inhomogenities present in amorphous solids and to observe narrow spectroscopic features in the presence of site inhomogeneous broadening (55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65)(66). The similarities between FLN and NPHB occur because both processes share a common first step, the site-excitationselection step.…”

“…The persistence of holes and the effects of laser power actually vary widely. The holes observed in a vibrational band of difluoroethane decreased with time at Tg (61,62), which was shown to be a thermal effect due to the background thermal radiation. Nonphotochemical holes burned in dimethyl-s^-tetrazine in polyvinylcarbazole also disappeared with time and showed broadening at relatively low laser powers (< 40 mW) (28).…”

“…Hereafter the term site-selection will be used, with the under standing that the sites are being excitation energy selected. ^The hole burning reported by Dubs and Gunthard (61,62) in rare gas matrices was done on vibrational bands from which fluorescence does not occur. Most examples of NPHB occur in electronic transitions and such hole burning has not been observed in rare gas matrices.…”