Radiation, highly coherent, spectroscopy lasers

Hepburn J W 1995 Generation of coherent vacuum ultraviolet radiation applications to high-resolution photoionization and photoelectron spectroscopy Laser Techniques in Chemistry vol 23, ed A B Myers and T R Rizzo (New York Wley) pp 149-83... 

In 1970 the first report of the molecular hydrogen laser opened up a decade of activity in VUV laser development, which included the appearance of rare gas excimer and exciplex lasers and the achievement of tunable coherent radiation in the Lyman-a region via harmonic generation. The surge of activity in the development of VUV lasers arose in part from the uniqueness of the VUV region, in part from the ultimate interest in X-ray lasers and, from our perspective, from the exciting prospects in spectroscopy and molecular dynamics promised by narrow linewidth, tunable, high-power VUV laser pulses for state-selective studies. Here we review the principles on which VUV lasers are based. 

Most of the vibrational and rotational spectra obtained before the second world war were measured using Raman methods. Interest in Raman then declined as infrared and microwave absorption instrumentation developed, but the introduction of visible lasers in the early 1960s has led to dramatic renaissance in Raman spectroscopy. As well as decreasing the acquisition time and increasing the sensitivity of conventional Raman spectra by orders of magnitude, the high power and coherence properties of laser radiation has spawned a host of new nonlinear Raman spectroscopies, some of which can be performed without a... 

While generation of sum frequencies yields tunable ultraviolet radiation by mixing the output from two lasers in the visible range, the phase-matched generation of difference frequencies allows one to construct tunable coherent infrared sources. One early example is the difference-frequency spectrometer of Pine [5.277], which has proved to be very useful for high-resolution infrared spectroscopy. 

In modern spectroscopy, it is necessary to have access to good sources of light, ultraviolet (UV), and infrared (IR) radiation. The laser is useful since it anits coherent EM radiation at a very high intensity and, if necessary, in a narrow frequency range. 

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