Nanosecond pulses

So far powerful lasers with picosecond to nanosecond pulse duration have usually been used for the ablation of material from a solid sample. The very first results from application of the lasers with femtosecond pulse duration were published only quite recently. The ablation thresholds vary within a pretty wide interval of laser fluences of 0.1-10 J cm , depending on the type of a sample, the wavelength of the laser, and the pulse duration. Different advanced laser systems have been tested for LA ... 

Rao reported measurement of third-order optical non-linearity in the nanosecond and picosecond domains for phosphorus tetratolyl porphyrins bearing two hydroxyl groups in apical position [89]. Strong nonlinear absorption was found at both 532 nm and 600 nm. The high value of nonlinearity for nanosecond pulses is attributed to higher exited singlet and triplet states. Time resolved studies indicate an ultra-fast temporal evolution of the nonlinearity in this compound. 

Intense nanosecond pulses (Ins = 10 9s) can be produced by Q-switching. A shutter is placed between the laser rod and one of the mirrors, thus inhibiting lasing. If the shutter is suddenly opened, the excitation is dumped in one huge burst. One type of shutter is the electro-optic Pockels cell (KH2P04 crystal with a high applied potential). 

The measurement of fluorescence life-times has great value for probing structural features of proteins. It requires expensive equipment since very rapid extinction of the exciting nanosecond pulse is necessary and the rapid decay of the emission must then be measured. The decay of the tryptophan fluorescence of LADH is biphasic with x = 3.9 and 7.2 ns and these are assigned to buried Trp-314 and exposed Trp-15, respectively. ... 

Recently, by using improved nanosecond pulse radiolysis with the monitoring wavelength region from 300 to 1600 nm [44], absorption spectra due to main reactive intermediates such as the intramolecular dimer cation radical in the near-IR wavelength region were clearly observed in the pulse radiolysis of polystyrene in various solutions [47]. For example. Fig. 1 shows the absorption spectra observed in the pulse radiolysis of polystyrene solutions in CH2CI2. 

Very intense and sharp near-UV absorption bands due to radical ions of polysilanes [53a,b] and polygermanes [53c] were observed by nanosecond pulse radiolysis. Broad visible and IR absorption spectra due to the radical ions of polysilyne [54] and polygermyne [54] were also observed. Very systematic pulse radiolysis studies on many different kinds of polysilanes [55] have been made by our improved nanosecond pulse radiolysis system over a wide range of... 

Figure 5 Transient absorption spectra of irradiated additive-free solid PMMA containing MMA monomers observed by the authors improved nanosecond pulse radiolysis system over a wide range of temperatures and with the monitoring wavelength region from 300 to 1600 nm.

Another study of scintillator fluorescence from 2,5-diphenyloxazole excited by sub-nanosecond pulses of electrons in cyclohexane or toluene has been made by Katsumura et al. [179]. They found that the emission intensity of fluorescence grew in two stages, a faster process occurring during the electron pulse (10 ps) and a slower process following the... 

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