Saturated absorption spectroscopy constant

B. Bobin, C.J. Bord6, J. Borde, C. Breant, Vibration-rotation molecular constants for the ground and (V3 = 1) states of SFg from saturated absorption spectroscopy. J. Mol. Spectrosc. 121, 91 (1987)... 

In contrast, emission from [Rh(bipy)2X2] is from a metal-centered, d-d) state. The various low-lying excited states for [Rh(bipy)2Cl2] are represented in Figure 3, with initial excitation into the (ti-te ) ligand state followed by relaxation and eventual phosphorescence from the d-d) state. The rise times for phosphoresence were reported to be 350-630 ns in room temperature solution and at 77 but these values were later found to be artifacts of the detection system. " The emitting dr-d) states of [Rh(bipy)2X2] absorb at 580 (X = Cl) and 550 nm (X = Br), and the lifetimes of their transient absorptions (measured by time-resolved absorption spectroscopy in air-saturated ethanol-methanol (4 1) solution at room temperature) were found to be 84 ns (X = Cl) and 54 ns (X = Br). " (If the solutions are deoxygenated, the lifetimes increase by about a factor of five.) The presumed relaxation path is represented in equation (147), with the rate of internal conversion (IC) a 4 X 10 " s ", followed by intersystem crossing (ISC), localized within the rf-manifold, with the rate constant ca. 8 x 10. 

Samples were prepared by exposing the silica gel, previously dried at 150°C for 24 h, to either cyclohexane or pentane solutions ctmtaining selected amounts of the fluorophore. The solvent was carefidly removed under vacuum when required. Complete probe adsorption of liquid-solid samples was verified with absorption spectroscopy. Less than 0.07% of the silica surface was typically covered by the probe. Immediately before data collection, dry samples were evacuated under vacuum at 125-130°C for 30 min. The total dehydration procedure was sufficient to remove the physisorbed water while leaving the surface silanol functionality intact [12]. Selected amounts of oxygen were introduced into a constant-position sample call by a series of stopcock manipulations and a vacuum line. Liquid-solid samples were deoxygenated ([O2]final < 10 M) by bubbling the samples with solvent-saturated nitrogen for 30 min. 

Another important nuclear characteristic is the nuclear quadrupole moment which, possessed by nuclei for which 7 1, has given rise to the important field of nuclear quadrupole resonance spectroscopy. A major importance of the quadrupole moment with respect to NMR absorption resides in the effects of quadrupole coupling constants on nuclear relaxation times and, therefore, on the line widths and saturation characteristics of NMR absorption (9). In addition, in favorable situations, quadrupole coupling constants can be derived from the characteristics of nuclear resonance of quadrupolar nuclei 127). Some examples of these effects will be described in Sections III, IV and VI of this chapter. 

Bor et al performed studies based on the generation of flavonoid radicals (aroxyl radical) by pulse radiolysis [138, 157, 158], The observations of fast absorption changes with kinetic spectroscopy allowed the determination of the ratio of the constants, which were obtained with several oxidizing radicals of flavonols such as kaempferol and quercetin. These studies revealed on the one hand that B-ring-localized semiquinones are the major radical species observed after univalent oxidation of dihydroflavonols, flavanones, and flavanols. Simultaneously revealed on the other hand was that a saturated 2,3 bond leads to a break of the 7t-electron system between the carbonyl group and the B-ring The presence of a 2,3-double bond (flavones and flavonols) led to a dislocation of the scavenged electron across the flavonoid structure. Such... 

Furthermore, using methyl orange (MO) and methylene blue (MB) as absorption probes, the micropolarity of the microemulsion system was investigated by UV-Vis spectroscopy [11]. The results demonstrated that micropolarity increased with the addition of IL only before the IL pools were formed. Once the IL was saturated for the solubilizing ability of the EO units and began to form cores of the microemulsions, the micropolarity became relatively constant. 

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