VUV laser radiation

Figure 4. Fe cluster ionization thresholds as a function of cluster size, as determined by photoionization yield measurements using tunable UV/VUV laser radiation.

Projection imaging with DUV (193 nm) and VUV (157 nm) excimer laser radiation was demonstrated by Ehrlich et al. (215). The optical system makes... 

Normal pulsed lasers, chopped cw laser radiation, or mode-locked dye lasers can be used for the generation of the light pulses. The output powers of the cw and mode locked lasers are rather low and they can be applied only in the visible or, after frequency doubling, in the UV spectral region [35]. They can be used for lifetime measurements with high accuracy [36] Only radiation from pulsed lasers can be transformed down to the VUV spectral region by using nonlinear effects. 

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. 

The powerful VUV generated by resonant frequency mixing is suited for applications which require very intense laser radiation like the multiphoton excitation of atoms and molecules, photodissociation studies of molecules or plasma diagnostics. 

Figure 6.20 Narrow-band VUV laser source. The upper part displays the generation of amplified NIR pulses from two cw ring Thsapphire lasers with pulse amplification in a multipass amplifier arrangement. The middle part shows the KDP and BBO crystals for sum-frequency generation. The VUV radiation is generated in a Xe jet shown in the lower part [589]...

Fig. 10.5 Schemes for resonance molecular photoionization via high-lying vibrational states by way of multiphoton resonance vibrational excitation with IR laser radiation (a) multiphoton IR + VUV excitation, (b) IR multiphoton excitation, and (c) IR multistep + VUV excitation.

For ion TOF measurement a probe laser was used to ionize reaction products in the reaction zone. The (1 + F) resonance-enhanced multiphoton ionization (REMPI) method was adapted for H-atom detection. The necessary vacuum ultraviolet (VUV) radiation near 121.6 nm (for Lyman-a transition) can readily be generated by a frequency-tripling technique in a Kr cell.37 The sensitivity of this (1 +1 ) REMPI detection scheme is extremely high owing to the large absorption cross-section of Lyman-a transition,... 

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