Photoionization representative laser

Reactions (19)-(21) represent the dissociation of benzene and reactions (22)-(26) represent the detection of fragments by VUV laser photoionization. The line-shape images resulted from these reactions. 

Figure 5-17. Photoionization threshold energy spectra for DABCO(CH3OCH3) and DABCO(TEA)i (2p3s) Rydberg state. Excitation is at the cluster first observed origin transition. The values of At represent the time delay between the excitation laser and the ionization laser.

LEI has been applied successfully to the trace determination of T1 [674] for certification purposes, and for combinations with laser evaporation and all other atomization techniques represents a powerful approach to detection. Laser photoionization and galvanic detection have been applied to hollow cathode dark space diagnostics [675]. Photoionization is produced to measure the dark space widths of linear field distributions directly. A theoretical model has been developed and its predictions verified with experimental findings for a uranium hollow cathode discharge operated in neon or xenon. Variations in the ground-state densities of sputtered neutrals have also been measured. 

Table I. Representative stepwise laser photoionization threshold results...

We can indeed claim that this is an example of photoselective laser chemistry. The competition between relaxation and reaction of photoex-cited electrons in clusters represented in Fig. 14(b) is reminiscent of the competition in many laser-induced chemical processes, stimulated by the selective absorption of one or more photons, such as photodissociation, photoionization, isomerization, and so forth in polyatomic molecules, where the coupling of many vibrational modes provides energy randomization and relaxation on picosecond time scales. 

Fig. 2. Energy diagrams schematically representing photoionization processes from the atomic ground state (a) single-photon ionization resulting from the absorption of one high-frequency UV photon (here it is the 13th harmonic of an IR laser) (b) ATI multiphoton ionization occurring in the presence of an intense IR laser (c) two-colour ionization occurring in the simultaneous presence of the IR laser and of the UV harmonic...

Fig. 3. A Risetime of absorption at 720 and 1230 nm. The smooth lines represent the computer best fits assuming an appearance time of 110 fs for the infrared specie (1230 nm) and its relaxation toward the solvated state in 2 0 fs. B Transient absorption spectra of the electron at 200 fs and 2ps following photoionization of pure liquid water with 100 fs laser pulse (A=310 nm, eV).

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