Probe tuning curve

Fig. 6.99 (a) Potential diagram of Nal with the pump transition at ki and the tunable probe pulse at k2(R). (b) Fluorescence intensity /fi(AO as a function of the delay time At between pump and probe pulses (curve a) with k2 tuned to the atomic Na transition and (curve b) k2 tuned to k2(R) with R < Rc [S19]... 

One-dimensional proton NMR spectroscopy is the most straightforward method for process validation and development. It can be used as a limit test, i.e., to demonstrate that a particular analyte is below the detection limit. It can also be used to accurately quantify an analyte by comparing the NMR peak area from a test sample against a standard curve. To get accurate quantitation, it is important to keep the acquisition parameters and conditions constant for both standard and test samples. For example, the receiver gain, power level, and duration of all pulses must stay the same within an assay. In addition, the probe should remain tuned for all samples. 

Figure 5-9. TRSEP signal for the aniline(N2)i cluster. Excitation laser is tuned to the TJj transition, and the probe laser is tuned to the I 6a transition. This plot shows the extent to which the probe pulse diminishes the total fluoresence. The time axis is the difference between the arrival times of the pump and probe pulses. The maximum diminution of the fluorescence is about 30%. The smooth curve is generated using the results of a nonlinear fitting routine. The fast component time constant is 200 + 50 ps.

Figure 1. Ionization charge as a function of the distance between the probes. The probe in contact with the laser beam ("beamprobe") is kept in a fixed position. Upper curve, beamprobe negative lower curve, polarity of probes reversed. Laser tuned to 3Sl/lt - 3P /t transition. Power density of the laser pulse is 7 X 10 W/ cm2 diameter of laser beam is 3 mm.

The molecule ABC is excited by a pump photon hv into the dissociating state with a potential curve Vi(/ ). A second probe laser pulse with a tunable wavelength X2 is applied with the time delay A . If X2 is tuned to a value that matches the potential energy difference hv = V2 R) — Vi(/ ) at a selected distance R between A and the center of BC, the probe radiation absorption a(X2, At) shows a time dependence, as schematically depicted in Fig. 10.13b. When X2 is tuned to the transition BC (BC) = V2(R = 00) — yi(/ = 00) of the completely separated fragment BC, the curve in Fig. 10.31c is expected. These signals yield the velocity v(R) of the dissociation products from which the energy difference V2( ) i( ) be derived. 

The average depolarization lifetimes t, plotted as open circles versus pump-probe wavelength in Fig. 2, increase from 5 to 12 ps as the wavelength is tuned to the blue from 675 to 660 nm. We have simulated this dependence by modeling the PS I core antenna absorption spectrum with Gaussian curve analysis of the Chi a Qy absorption spectrum of highly enriched PS I particles [7]. According to Forster theory, EET from Chi a spectral component i to spectral component j in the core antenna will occur with rate proportional to... 

Figure 24.14 Ion signals for Ba FCH3 (a) and BaF(b) as a function of the delay time t between the pump pulse at 618 nm and probe pulse at 400 nm. The solid lines represent the theoretical fit curves, which in (b) were obtained by superposition of two contributions (dashed and dotted lines). In (c), the pump wavelength is tuned off-resonantto 636 nm thus, the Ba FCFI signal represents the cross-correlation curve of the laser pulses for the width tl = 130 fs. Reproduced from Farmanara etat Chem. Phys. Lett., 1999, 304 127, with permission of Elsevier...

The relaxation curve is then probed point-bypoint by switching the field up to the detection field level and by acquiring the NMR signal using a RF pulse or an echo RF pulse sequence. The detection field is chosen as high as possible, and is the same for all experiments. This is the field to which the RF console is tuned. The amplitude of the NMR signal represents the magnetization at the end of the evolution interval, in which relaxation takes place. Thus... 

Fig. 12.15. Experimental demonstration of the nearly complete depletion of a molecular level in a collision-free molecular beam. The probe laser is stabilized on the (v =0,J =28) - (v =6,J =27) transition. The pump laser is tuned. The lower curve is the excitation spectrum of the pump laser, the upper curve shows the fluorescence intensity of the probe laser, which drops nearly to zero when the pump is tuned to the (0,28) ->(17,27) transition.

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