Laser-irradiation

For the techniques using very short, high irradiance laser pulses, a more or less smooth transition to pyrolysis of the sample is observed with increasing irradiance. It appears that at least for the LAMMA technique this transition does not always occur at identical irradiances for positive and negative ions. This will be discussed in more detail later in this paper. 

Fig. 25 TEM images revealing (a) rolling of an exfoliated GnS layer and (b) GaS nanotubes obtained by solvent irradiated laser irradiation.

Muniz-Miranda M, Ottaviani ME (2004) Silver nanoclusters in mesoporous silica, as obtained by visible-laser irradiation. Laser Phys 14 1533-1538... 

The laser irradiance (laser power/cm2) is an important parameter Different irradiance values lead to a vapor cloud of different density, and consequently the ion-molecule reactions can take place with highly different yields. 

The D-band is observed at ca. 1347 cm . It results from disorder defects in the nanotube lattice and originates from phonons close to the point K of the Brillouin zone. The signal is strongly dependent on the irradiated laser energy. Changing,... 

Miller l.D. and Veitch A.R. 1993. Optical modehng of hght distributions in skin tissue following laser irradiation. Lasers Surg. Med. 13 565. 

It is well known that high-quality three-dimensional photonic stmctures, e.g., buried chaimel waveguides, which can be used for laser emissions, have been readily created on transparent laser ceramics, by using irradiations of short-pulse lasers [263-271] and particle beams [272—278]. This process is based on the controlled modification of the refractive index of the electronic processes and thermally induced transformations associated with laser irradiation. Laser writing to create such structures is a one-step process without the requirement of special preparation. It is a very fast, highly reproductive, and thus low-cost process. It has been employed to fabricate various integrated photonic devices. 

Because the irradiating laser beam is pulsed, MALDI is optimally combined with a TOP mass analyzer. The unlimited mass range of TOP and its ability to acquire the entire spectrum from a single laser pulse event are other factors in favor of the MALDI/TOF-MS combination. MALDI-TOF has become a well-known acronym for many researchers. Quadrupole, ion trap, and Fourier transform ion cyclotron resonance (FT-ICR) instruments have also been modified to accommodate MALDI. A schematic diagram of MALDI/TOF-MS is presented in Figure 2.10. A variety of laser systems has found applications in MALDI analysis, and the most common ones use LTV lasers such as the N2 laser (337 nm), the frequency-tripled (355 nm) and frequency-quadrupled (266 nm) Nd YAG laser, and the ArF excimer laser (193 nm). IR lasers have also been used to produce the MALDI effect. The transversely excited atmospheric (TEA) CO2 laser (10.6 p,m), the Q-switched Er YAG laser (2.94 (im), and the CriLiSAF or Nd YAG pumped optical parametric oscillator (OPO) laser (3.28 p,m) are the common IR lasers. UV and IR lasers yield similar spectra for proteins, although better resolution has been obtained for some proteins with an IR laser. 

FOU 88] Fouassier J.P., Chesneau E., Polymerisation induite sous irradiation laser visible, 3. Un nouveau systeme photosensible performant ,... 

Another method for the formation of particles with a specified velocity vector is based on photodissociation processes. So, it is known that hot hydrogen atoms can be obtained by laser photolysis of HI and HBr molecules using excimer lasers. In this process, the energy of the translational motion of the H atom depends on the wavelength of the irradiating laser radiation. 

Miranda etaL reported that irradiation (254-nm mercury lamp) of [3.2]PCP-2-one 16 in benzene led to [2.2] PCP 15 as the only product via acyl-alkyl biradical 32 and biradical 33. A laser-flash photolysis study (266 nm) of 16 in cyclohexane indicated that biradical 33 is detectable at room temperature and does not cleave to p-xylylene 35 but cycKzes to [2.2]PCP 15 or dimerizes to [2 ]PCP 34. Irradiation (laser, 308 nm) of a cyclohexane solution of 15 containing a triplet quencher (cyclooctadiene) showed two absorption maxima, which correspond to p-xylylene 35 and the hiradical 33. The cyclophanes [2 ]PCP 21 and [2 ]PCP 34 were formed by irradiation (laser, 248 or 266 nm) of cyclohexane solutions of [2.2]PCP 15. While the formation of 34 agrees well with the intermediacy of 33, the detection of [2 ] PCP 21 provided further evidence for the intermediacy of p-xylylene 35, which can couple either its tiimeric or tetrameric products. 

---