Pulsed lasers nitrogen

Figure 3. IR spectra of a polyester-acrylate photoresist exposed for various times to nitrogen-laser pulses in the presence of air. (--- polyurethane-acrylate).

Typical decay curves of benzophenone (BP) phosphorescence (analyzed at 450 nm) at various temperatures in PMMA excited by a 10-ns nitrogen laser pulse at 337 nm are shown in Fig. 1 (6). The phosphorescence intensity, l(t), decreases as a single exponential below the temperature corresponding to the ester side-group rotation (Tq = -3O C for PMMA). Deviations from a single-exponential decay are observed for T>Tg, which increase with increasing temperature, but the deviation becomes less marked above the glass transition temperature, T, of the matrix polymer and disappears at 15O C. 

Figure 1. Semilogarithmic decay curves of benzophenone phosphorescence in PMMA excited by 10-ns nitrogen laser pulse at 337 nm. Temperature and symbols for time scales are given beside the curves. (Reproduced from Reference 6. Copyright 1984 American Chemical Society.

The phosphorescence of BP (0.17 ) in poly(vinyl alcohol) (PVA) film (250 micron thickness) excited by a 10-ns nitrogen laser pulse at 337 nm decays exponentially for T < T (-100°C) or T > T (85°C), but deviates from single exponential for T < T < T. The eviation was attributed to the diffusion-controlled hydrogen abstractlon reaction between benzophenone triplet and the PVA matrix (33). 

The non-exponential decay of benzophenone phosphorescence in PMMA at room temperature was also observed by Fraser et al. (36), under the condition of repeated irradiation of a nitrogen laser pulse, and they proposed a triplet-triplet annihilation mechanism in which the polymer matrix itself participated as an energy acceptor from benzophenone triplet and a medium for the triplet energy migration. 

The excimer laser radiation is pulsed with a typical maximum rate of about 200 FIz. Peak power of up to 5 MW is high compared with that of a nitrogen laser. 

C07-0047. A nitrogen laser puts out a pulse containing 10.0 mJ of energy at a wavelength of 337.1 nm. How many photons is this ... 

Figure 5 shows the dependence of the total emission intensity on the excitation intensity and its spectral width obtained from DCM-encapsulated dendrimers. A nitrogen laser (wavelength of 337 run, pulse duration of 4 ns, and repetition rate of 10 Hz) was used as the excitation source. A cylindrical lens focused the excitation beam onto a stripe 200 pm wide on a quartz cuvette... 

Photolysis of the 2-fluorenyl azide precursor compound by the 267 nm pump laser pulse releases a nitrogen molecule and produces the singlet 2-fluorenylnitrene intermediate as shown in Scheme 3.2. In the presence of appreciable amounts of water, this singlet 2-fluorenylnitrene species can react with the water molecule to form a singlet 2-fluorenylnitrenium ion and an OH species as shown in Scheme 3.2. 

For the investigation of triplet state properties a laser flash photolysis apparatus was used. The excitation source was a Lambda Physik 1 M 50A nitrogen laser which furnished pulses of 3.5 ns half-width and 2 mJ energy. The fluorescence decay times were measured with the phase fluorimeter developed by Hauser et al. (11). 

The initiation system consists of a nitrogen laser and the necessary optics to lead the beam to the sample cell. The laser emits pulses at 337.1 nm with 800 ps duration, with a typical repetition rate of less than 5 Hz. The optical components, aligned between the laser and the calorimetric cell, consist of an iris (I), a support for neutral density filters (F), and a collimating lens (L). The iris is used to cut out most of the laser output and allow only a thin cylinder of light to pass through its aperture, set to 2 mm. The laser energy that reaches the cell is further... 

Matrix assisted laser desorption ionization time-of-flight (MALDI-TOE) mass spectrometry was carried out with a PerSeptive Biosystems Voyager-DE-RP MALDl-TOF mass spectrometer. A 337-nm UV nitrogen laser producing 3-ns pulses was used in the reflectron mode. The samples were prepared by mixing 10 pi of a 0.1 M HAc solution of the sample with 20 pi of a solution of 3 mg/1 a-cyano-4-hydroxy cinnamic acid in wafer. One pi of that solution was loaded on the gold-sample plate. 

Light pulses with halfwidths of 10" sec have been generated mainly by Q-switched solid-state lasers but can be obtained principally with all high-gain laser transitions, as for instance CO2 lasers " ), nitrogen lasers ) (X = 3300 A), or dye lasers ). 

After introduction of the target into the vacuum, an UV laser pulse is used to desorb and ionize the sample. Nitrogen laser emitting at 337 nm and Nd YAG laser emitting at 355 nm are the most widely used. MALDI is a very powerful technique for the analysis of synthetics and natural biopolymers. It has completely replaced former techniques such as fast atom bombardment (FAB). In... 

Figure 1. Fluorescence spectra (uncorrected for the spectral response) of ZnTPP in EPA at room temperature taken by the 540 nm excitation of a nitrogen pumped dye laser, (a)normal fluorescence spectra, (b)delayed fluorescence spectra taken at 1 s after the laser pulse excitation.

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