Multiphonon produced

A very common heating sensing technique used in condensed matter is photoacoustic (PA) spectroscopy, which is based on detection of the acoustic waves that are generated after a pulse of light is absorbed by a luminescent system. These acoustic waves are produced in the whole solid sample and in the coupling medium adjacent to the sample as a result of the heat delivered by multiphonon relaxation processes. 

Indirect transfer occurs by a two-part mechanism, as shown in Fig. 18. First a vibrational excitation decays by generating phonons. The phonons then produce vibrational excitation on other molecules by multiphonon up-pumping. Indirect transfer will not occur unless the density of vibrational excitations is large enough to produce a real increase in the bath temperature. 

Picosecond laser pulses in the UV range do not result in better ablation behavior than nanosecond laser pulses. This is different for doped polymers. Experiments with doped PMMA (an IR-absorber, i.e., IR-165 for ablation with near-IR laser and diazomeldrum s acid (DMA) for ablation with UV lasers) with nanosecond and picosecond laser irradiation in the UV (266 nm) and near-IR (1064 nm) range have shown that, in the IR, neat features could be produced with picosecond laser irradiation, while nanosecond irradiation only results in rough surface features [105]. This corresponds well with the different behavior of the two absorbers. With IR-165 the polymer is matrix is heated by a fast vibrational relaxation and multiphonon up-pumping [106]. This leads to a higher temperature jump for the picosecond irradiation, which causes ablation, while for nanosecond pulses only lower temperatures are reached. 

Multiphonon relaxation from the emitting Dq and D4 states of europium and terbium that arise from interaction with water of residual alcohol (formed as a result of the reaction producing the glass) and are decreased strongly in the complex and especially in sol-gel. 

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