Wavelengths action spectroscopy

The temporal structure of PEL radiation typically consists of ps-long macropulses, which are made up of a train of ps-long micropulses at MHz to GHz repetition rates. Other parameters of the CLIO and FELIX FELs are collected in Table 1 [189, 190]. At the FELIX facility, an FEL for wavelengths between 100 im and 1.5 mm has been constracted (FLARE). Other tunable infrared FELs in use for action spectroscopy applications are located at the Tokyo University of Science and the Fritz-Haber Institute in Berlin their specifications are comparable to those listed for FELIX and CLIO in Table 1. 

With stringent precautions to avoid the presence of water, polycyclic aromatic hydrocarbons show two one-electron reversible waves on cyclic voltammetry in dimethylformamide (Table 7.1). These are due to sequential one-electron additions to the lowest unoccupied molecular n-orbital [1]. Hydrocarbons with a single benzene ring are reduced at very negative potentials outside the accessible range in this solvent. Radical-anions of polycyclic aromatic hydrocarbons [2] and also alkyl benzenes [3] were first obtained by the action of alkali metals on a solution of the hydrocarbon in tetrahydrofuran. They have been well characterised by esr spectroscopy. The radical-anions form coloured solutions with absorption bands at longer wavelength than the parent hydrocarbon [4,5]. 

Deb and Yoffe [134] examined the decomposition of thallous azide under the action of ultra-violet light in the wavelength region 3200-3800 A. Two exciton bands 3415 and 3348 A have been observed in thallous azide by low-temperature spectroscopy (Nikitine and Gross s method). The refractive index has been measured by the Brewster angle method, the electron energy levels have been estimated and the results of the photochemical decomposition have been related to the electron energy level and to measurement of photoconductivity [33],... 

To confirm that the transient fluorescence is indeed an action signal due to resonant infrared absorption, the fluorescence intensity in the image was measured as a function of IR wavelength (TFD-IR spectroscopy, [27]). Figure 29.4e shows the TFD-IR spectrum of Rhodamine-6G. When the IR wavelength was scanned over the... 

In view of the ease and success of lasing lanthanide ions, only some compelling reason such as the requirement of a specific wavelength would warrant development of some of the actinide lasing schemes discussed. Perhaps additional spectroscopy will reveal advantages of using actinide ions in other valence states and hosts for efficient laser action. 

The harmonics are particularly attractive in terms of the radiation peak power. Thus, it should open the way for non-linear laser spectroscopy in the short-wavelength (10 nm) regime. A competing technology requiring much larger installations is Self Amplified Spontaneous Emission used for Free-Electron-Laser action (SASE-raL) [25,26]. 

Visible and UV light sources, which excite electronic transitions, can be used also for PD spectroscopy. By scanning the frequencies of the radiation emitted from the UV/vis light source and measuring PD or electron photodetachment as a function of excitation wavelength, an electronic action spectrum can be constructed in the same way as a vibrational action spectrum is constructed using an IR source. 

Another advantage of this method is the possibility of carrying out the reaction dynamics studies using frequency- or time-domain spectroscopy. In the former implementation, both photodepletion and action spectra can be measured, depending upon the types of measurement employed. In photodepletion studies, one measures the complex depletion as a function of the excitation laser wavelength. The complex signal is... 

Difference spectroscopy showed that the extract contained the hemo-proteins P-450 and cytochrome 65. Of special interest is the inhibition of 6 -hydroxylase activity by CO and the reversal of this inhibition by light, suggesting that P-450 may be involved in the reaction. In a subsequent experiment, the 6,.3-hydroxylase activity was assayed in the presence and absence of CO, and under light of various wavelengths between 400-500 m//. Reactivation of the CO inhibited enzyme was maximum at 450 mix. An action spectrum obtained from these data exhibited a maximum at 450 mu and minima at 400 and 500 m//, closely resembling the absorption spectrum of the P-450 CO complex [Voigt (62)]. It thus appears that the 6j3-hydroxylase system, like several other steroid hydroxylases, requires the participation of microsomal electron transport with P-450 as the terminal oxidase. 

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