Near-infrared irradiation

M. Uo et al. reported on a dental composite resin cured under near-infrared irradiation. They showed the following composite resin (CR). The mixture of Bis-GMA and TEGDMA was used as the base resin matrix. Bis-GMA and TEGDMA are mixed to be 2 1 in weight ratio. 

Chen CC, Lin YP, Wang CW et al (2006) DNA-gold nanorod conjugates for remote control of localized gene expression by near infrared irradiation. J Am Chem Soc 128 3709-3715... 

DNA Gold nanorod conjugates for remote control of localized gene expression by near infrared irradiation. 

As shown in Fig. 21.12, after X-ray irradiation, the BaBPOs crystal shows a few broad, distinct absorption bands from near-infrared to the band gap in the VUV, which indicates the presence of some trapping sites in the crystal and... 

Figure 7.3 shows the two-beam photon-force measurement system using a coaxial illumination photon force measurement system. Two microparticles dispersed in a liquid are optically trapped by two focused near-infrared beams ( 1 pm spot size) of a CW Nd YAG laser under an optical microscope (1064 nm, 1.2 MWcm , lOOX oil-immersion objective, NA = 1.4). The particles are positioned sufficiently far from the surface of a glass slide in order to neglect the interaction between the particles and the substrate. Green and red beams from a green LD laser (532 nm, 21 kWcm ) and a He-Ne laser (632.8 nm, 21 kW cm ) are introduced coaxially into the microscope and slightly focused onto each microparticle as an illumination light (the irradiated area was about 3 pm in diameter). The sizes of the illumination areas for the green and red beams are almost the same as the diameter of the microparticles (see Figure 7.4). The back scattered light from the surface of each microparticle is...

The oxide CeC>2 doped with approximately 1% Er3+ exhibits up-conversion involving only one active ion. The Er3+ ions substitute for Ce4+ to form a low concentration of Erte defects randomly distributed within the oxide matrix. Irradiation with near-infrared photons with a wavelength of 785 nm excites the Er3+ ions from the 4Ii5/2 ground state to the 4I9/2 level, that is, a GSA mechanism ... 

Even more elegantly, the local resolution is improved by irradiation with very intense focused femtosecond laser pulses outside the absorption range of the fluoro-phore (e.g., in the near-infrared). The very intense focus of the laser beam—and only this—will excite the fluorophore by nonresonant two-photon absorption. Artifacts by scattered primary radiation are ruled out and the local resolution is comparable to a confocal microscope. In addition, the damage of the sample by laser light absorption is reduced to a minimum. 

Experiments were conducted in our laboratory to evaluate many of the dynamical expectations for rapid laser heating of metals. One of the aims of this work was to identify those population distributions which were characteristic of thermally activated desorption processes as opposed to desorption processes which were driven by nontbennal energy sources. Visible and near-infrared laser pulses of nominally 10 ns duration were used to heat the substrate in a nonspecific fashion. Initial experiments were performed by Burgess etal. for the laser-induced desorption of NO from Pt(foil). Operating with a chamber base pressure 2 x 10 torr and with the sample at 200 K, initial irradiation of a freshly cleaned and dosed sample resulted in a short time transient (i.e. heightened desorption yield) followed by nearly steady state LID signals. The desorption yields slowly decreased with time due to depletion of the adsorbate layer at the rate of ca. 10 monolayer... 

The observations of complex dynamics associated with electron-stimulated desorption or desorption driven by resonant excitation to repulsive electronic states are not unexpected. Their similarity to the dynamics observed in the visible and near-infrared LID illustrate the need for a closer investigation of the physical relaxation mechanisms of low energy electron/hole pairs in metals. When the time frame for reaction has been compressed to that of the 10 s laser pulse, many thermal processes will not effectively compete with the effects of transient low energy electrons or nonthermal phonons. It is these relaxation channels which might both play an important role in the physical or chemical processes driven by laser irradiation of surfaces, and provide dramatic insight into subtle details of molecule-surface dynamics. 

However, the high frequency of the laser irradiation in the visible region may lead to photochemical reactions in the laser focus. Besides, fluorescence can often cover the whole Raman spectrum. Such problems can be avoided by using an excitation wavelength in the near-infrared (NIR) region, e.g. with an Nd YAG laser operating at 1064 nm. Deficits arising from the v dependence of the Raman intensity and the lower sensitivity of NIR detectors are compensated by the Fourier-Transform (IT) technique, which is widespread in IR spectroscopy . ... 

COLOR CENTERS. Certain crystals, such as the alkali halides, can be colored by the introduction of excess alkali metal into the lattice, or by irradiation with x-rays, energetic electrons, etc. Thus sodium chloride acquires a yellow color and potassium chloride a blue-violet color. The absorption spectra of such crystals have definite absorption bands throughout the ultraviolet, visible and near-infrared regions. The term color center is applied to special electronic configurations in the solid. The simplest and best understood of these color centers is the F center. Color centers are basically lattice defects that absorb light. 

Important scientific and industrial applications for thulium and its compounds remain to be developed. In particular, the photoelectric, semiconductor, and thermoelectric properties of the element and compounds, particularly behavior in the near-infrared region of the spectrum, are being studied. Thulium has been used in phosphors, ferrite bubble devices, and catalysis. Irradiated thulium (169Tm) is used in a portable x-ray unit. 

The radical anion Cw, can also be easily obtained by photoinduced electron transfer from various strong electron donors such as tertiary amines, fer-rocenes, tetrathiafulvalenes, thiophenes, etc. In homogeneous systems back-electron transfer to the reactant pair plays a dominant role resulting in a extremely short lifetime of Qo. In these cases no net formation of Qo is observed. These problems were circumvented by Fukuzumi et al. by using NADH analogues as electron donors [154,155], In these cases selective one-electron reduction of C6o to Qo takes place by the irradiation of C6o with a Xe lamp (X > 540 nm) in a deaerated benzonitrile solution upon the addition of 1-benzyl-1,4-dihydronicoti-namide (BNAH) or the corresponding dimer [(BNA)2] (Scheme 15) [154], The formation of C60 is confirmed by the observation of the absorption band at 1080 nm in the near infrared (NIR) spectrum assigned to the fullerene radical cation. 

Low energy initiation techniques [179, 180, 181] (near infrared, ultrasonic radiation and line tuneable pulse laser) have lately emerged to be better alternatives to the high-energy radiations (y-irradiation and e-beam). Laser-induced polymerisation of monomers have attracted significant attention in recent years generating a considerable literature published on both pulsed... 

The alkane radical-cations generated in electron-pulse irradiated n-dodecane show an absorption band in the visible with its maximum at 800 nm (Fig. 15) [93], The position of the absorption maximum changed from 600 nm to 900 nm depending on the carbon number of the alkane. It was noted that the lifetime of alkane-radical cations was shorter than that of the solvated electrons observed in the near infrared region. These phenomena were interpreted in terms of the following ion-molecular reaction. 

A Raman spectrum is excited by irradiating a sample with coherent or non-coherent monochromatic radiation in the ultraviolet, the visible, or the near-infrared range. By an elementary process described in Sec. 2.4, the sample produces usually non-coherent radiation the strong Rayleigh line at the frequency of the exciting radiation and weak lines at frequencies. shifted from the frequency of the exciting radiation by definite quantities, the Raman spectrum. 

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