Laser excitation wavelength

In general, the choice of a laser for use as a Raman excitation source is based on a number of considerations. The laser excitation wavelength, for experimental and theoretical reasons, must lie in the visible region, i.e. 400-700 nm. The laser should have many emission lines over a wide range of the visible region and the excitation frequency should not correspond... 

Fig. 9 The LSCM images of Equsetum arvense microspores stained with colchicine 10 7 M. The laser excitation wavelength 458 nm.

Fig. 10 The LSCM images of Hippeastrum hybridum pollen tube stained with colchicine 10" 7 M. The laser excitation wavelength 458 nm. 1. The bright emission is observed in nucleus of vegetative cell of pollen and in the spermium located in the tip of the tube 2. Spermium in the tip of pollen tube. The microtubules contained of tubulin are seen. 

Figure 3 shows the 10-ns Raman spectra of Ni protoporphyrin in neat piperidine (>909S 6-coordinate form). The laser excitation wavelength of 420 nm preferentially excites the 6-coordinate form which happens to dominate the absorption at this wavelength (9-11). With respect to the low power spectrum, the spectrum obtained at high power shows increased intensity in the lines at 1660 ( q)>... 

Fig. 5.6. The absorption (gray bands) and emission (black bands) spectra of various fluorochromes. The wavelength widths of the bands for each fluorochrome indicate the range of wavelengths that will be absorbed and emitted. Laser (excitation) wavelengths are indicated at the bottom of the chart. From Shapiro (1995).

Figure 2. Frequencies of SER C-N stretching mode, VCN> plotted against electrode potential for Fe(CNg3-/4- adsorbed at gold electrode in supporting electrolytes containing various alkali metal cations. Solutions were 1 mM Fe(CN)g - or Fe(CN)g with 0.1 M MCI + 0.01 M HCIO4, where M = Na+, K, or Cs+ as indicated. Laser excitation wavelength was 647.1 nm.

Figure 2. Growth of the absorption due to the formation of (SCNV at intervals ranging from 40ns to 800ns after the laser pulse. (KrF laser, excitation wavelength 248nm, [H202]= 50mM, [SCN-] = 0.5mM)...

The rate constants for quenching of the triplet state of 3,4-dimethoxyacetophenone by methoxybenzene or phenol in benzene solution were determined using samples of 3,4-dimethoxyacetophenone with an absorbance of 0.1 (ca. 2 x 10 3 mol.1. 1) at the laser excitation wavelength (354.7 nm) in the presence and absence of the quenchers. Neither phenol nor methoxybenzene absorb at the laser excitation wavelength. 

Figure 21 Typical Lll courses of Ti02 with different laser excitation wavelengths (Leipertz and Dankers, 2003).

The experimental conditions for the excitation and detection of all the species are listed in Table I along with the radiative lifetimes of the excited states. Under the narrow detection bandwidth conditions for these measurements the quench term is much greater than T 1 for the species studied and the fluorescence efficiency varies as x T1/2. Thus with fixed geometry, laser excitation wavelength, and detection parameters, the fluorescence intensity in Equation (1) simplifies to... 

ZEKE-PES was pioneered by Miiller-Dethlefs, Sander and Schlag18,25. They and others26 recorded the zero kinetic energy photoelectrons produced by absorption of one or more photons to a resonant ion state as a function of pulsed laser excitation wavelength. ZEKE electrons were extracted by an electric field pulse which permitted a delay between the creation and collection of electrons. During this delay, non-ZEKE electrons departed the focal volume, leaving only ZEKE electrons for collection by the extraction pulse. 

TABLE 1 Laser excitation wavelengths suitable for excitation of l ... 

Fig. 12.2 Comparison of high- and low-frequency Raman spectra of SWCNTs, DWCNTs, and small-diameter MWCNTs. Spectra were recorded using 633-nm laser excitation wavelength...

Figure 12.5 shows the in situ Raman analysis of the low frequency RBM range for DWCNTs, acquired using three different laser excitation wavelengths. The intensity of the peaks between 220 and 280 cm decreases constantly during heating from room temperature to 400°C (Fig. 12.5a). Since there are no observable...

Following their first experiments devoted to 6-nitro-BIPS,17 Takahashi and co-workers conducted a series of nanosecond TR3 studies24-28 on a limited number of photochromic compounds, namely r,3, 3-trimethylspiro[2ff-l-benzo-pyran-2,2 -indoline] (BIPS), 6-nitro-BIPS, and spirobibenzopyran (SBP) (Scheme 4). This work was undertaken to elucidate the electronic distribution of the metastable photomerocyanines (ort/jo-quinoidal or zwitterionic) and the number of stereoisomers involved in the photochromic process. Therefore, the effects of temperature, solvent, laser excitation wavelengths, and isotopic substitutions (I3C and, 5N) on the resonance Raman spectra were intensively studied to clarify the photochromic mechanism in the compounds investigated. 

The data obtained in the infrared-diode-laser-probe studies described above provides quenching information at a given substrate donor energy E. By varying the laser excitation wavelength for production of vibrationally hot... 

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