One laser experiment

In the "one laser experiment (Figure 1), the ions were desorbed by a single laser pulse using a focussing lens. A mirror... 

Figure 11 Transient absorption spectra obtained following one-laser photolysis (355 nm ) and two-laser photolysis (355 + 590 nm ) of all-rrans-retinol in air-saturated acetonitrile. In the one-laser experiment, the spectrum was obtained 1.9 (xs following the 355 nm pulse. In the two-laser experiment, the spectrum was obtained 1.9 ps after the 355-nm pulse and 400 ns following the 590-nm pulse. The kinetic behaviors observed at 570 and 610 nm are also shown. (From Ref. 18.)...

Figure 9.22 illustrates how a CARS experiment might be carried out. In order to vary (vj — V2) in Equation (9.18) one laser wavenumber, Vj, is fixed and V2 is varied. Here, Vj is frequency-doubled Nd YAG laser radiation at 532 nm, and the V2 radiation is that of a dye laser which is pumped by the same Nd YAG laser. The two laser beams are focused with a lens L into the sample cell C making a small angle 2a with each other. The collimated CARS radiation emerges at an angle 3 a to the optic axis, is spatially filtered from Vj and V2... 

Equations (16) and (17) describe second-harmonic generation (SHG) and third-harmonic generation (THG) of one laser beam with a single polarization. Self-phase modulation (SPM) of a single laser beam is described in Eq.(18) as e.g. employed in z-scan experiments [6]. Equation (19) is the cross-phase modulation (XPM) process between two laser beams and Eq.(20) describes the four wave mixing with degenerate frequencies (DFWM). 

Due to the fact that lasers can be focused into a very small volume, small slits can be used together with a fast rotating disk to make the time resolution in the one-slit experiment in the tens of nanoseconds when using very sensitive detection techniques and samples with good Raman enhancements. This technique will probably be most useful in the microsecond time regime. Fig. 1 shows the results of this technique when used in the measurement of the time development of the bands characteristic of the intermediates produced in the bacteriorhodopsin photosynthetic cycle (8). Using optical flash photolysis (17) techniques, the rise time of the intermediate having a Raman band at 1570 cm l is known to be in the microsecond time scale. 

Figure 11-3. Effect of the pump laser at 250 nm with a time advance of 10 ns on the one laser REMPI spectrum of the probe laser [15]. Both spectra were recorded using the same intensity for the probe laser. The pump laser in the two laser experiment resulted in a maximum depletion of 20-25% in the region between 245 and 280 nm, and an enhancement of three decades at 220 nm. See text for a detailed explanation of the experimental method. (Reproduced with permission from J. Phys. Chem. 2004, 108, 943-949. Copyright 2004 American Chemical Society.)...

The experiment was performed with one laser used to excite the conversion to the high-spin state and a second to monitor the relaxation back to the low-spin state. This approach allowed measurements over the wide dynamic range from nanoseconds to seconds. Pressures up to 1 kbar were... 

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