Magnetic field effects fluorescence

Even more important are reactions of radiolytic products with the precursors of these excited states. Results from recent experiments in which the solute luminescence and magnetic field effect were compared for radiolysis of cyclohexane or isooctane with 0.5-2.2 MeV electrons, 1-5 MeV protons, and 2-20 MeV a-particles suggested that the decrease in the solute luminescence and the magnetic field effect was due to both the increasing importance of crossrecombination and the "intervention of radicals or other transient species with the precursors" with the fluorescent states [63]. The effects of spin relaxation and ion-radical reactions in dense spurs were identified as likely causes for reduced magnetic field effects, fluorescence yields, and probabilities 0 in spurs from 17-40 keV x-rays as compared to the spurs from fast electrons [80]. 

Little attention has been devoted to the effects of time-dependent magnetic fields (created by electromagnetic waves) in the absence of a strong magnetic field. Hore and his coworkers [123-125] recently described this effect as the oscillating magnetic field effect (OMFE) on the fluorescence of an exciplex formed in the photochemical reaction of anthracene with 1,3-dicyanobenzene over the frequency range 1-80 MHz. 

Conventional EPR techniques have been successfully used to measure the D and E values of matrix-isolated carbenes in the ground triplet state because the steady-state concentration of triplet species is sufficiently high in the system. The technique cannot be used, however, for excited species having triplet hfetimes of the order of 10-100 ns, since their steady-state concentration is too low. The D parameters are estimated from the external magnetic field effect on the T—T fluorescence decay in a hydrocarbon matrix at low temperamre. The method is based on the effect of the Zeeman mixing on the radiative and nonradiative decay rates of the T -Tq transition in the presence of a weak field. The D values are estimated by fitting the decay curve with that calculated for different D values. The D T ) values estimated for nonplanar DPC (ci symmetry) is 0.20... 

Auzinsh, M.P. (1987). Polarization of laser-excited fluorescence of diatomic molecules and the magnetic-field effect, Opt. Spectrosc. 

Due to the spin conserving rule, the rate constants of some excitonic interactions are subject to modulation by weak magnetic fields (less than IT). The magnetic field modulation of the singlet exciton fission rate [see Scheme (80)] can be experimentally observed as a magnetic field effect on prompt fluorescence [192,200,201,273-278]. The magnetic field sensitive triplet-triplet (80) and triplet-doublet (110) annihilation... 

Fig. 6-3. Magnetic field effects observed in the radiation reaction of a squalane (S) solution of fluorene (M) for pulse radiolysis with a 4-MeV electron accelerator. The reaction temperature is not described in the present papers, but may be room temperature, (a) Time profile of fluorine fluorescence during and after pulse radiolysis of a squalane solution (1) at the minimum field less than 0.05 mT, where the residual field of an electromagnet is cancelled by passing a small reverse current through the magnet s coils (2) at 0.3 T. (b) The time dependence of the magnetic field enhancement of the fluorescence intensity (A) 15-ns pulse ( ) 50-ns pulse, (c) The MFE on the increase in fluorescence intensity at 200 ns after the pulse. (Reproduced from Ref. [18b] by permission from The American Chemical Society)...

Magnetic field effects on delayed fluorescence from methylene chloride solutions ... 

Several applications have been proposed recently for the use of phenoth-iazines in various fields, such as materials chemistry [77,78], magnetic field effects on fullerene-phenothiazine linked compounds [79,80] and fluorescent labelling [81]. 

Because of their high intensity. X-ray tubes were commonly used as laboratory radiation sources for radiation chemistry experiments until they were superceded by particle accelerators during the middle part ofthe 20th Century. They still retain specialized uses in research applications such as being used as the radiation source for MARY (MAgnetic field effect on Reaction Yield) spectroscopy studies of radical cation lifetimes and reactivity in alkane solvents [14,18]. MARY spectroscopy uses fluorescence to detect variations in singlet-triplet dynamics in radical ion pairs as a function of magnetic field. It is particularly useful for short-lived transients that are difficult to study by ESR. 

Infra red spectra of triplet phenylnitrenes , zero-field splitting of the T, state in biradicals measured by magnetic field effects on fluorescence decay , and oiplet-triplet fluorescence and spin polarization of 1- and 2-naphthylphenylcarbenes ° are experimental studies reported on biradical species. 

Frank HA, McGann WJ, Machniki J and Felber M (1982b) Magnetic field effects on the fluorescence of two reaction centerless mutants of Rhodopseudomonas capsulata. Biochem Biophys Res Comm 106 1310-1317 Frank HA, Machnicki J and Friesner R (1983) Energy transfer between the primary donor bacteriochlorophyll and carotenoids in Rhodopseudomonas sphaeroides. Photochem Photobiol 38 451-455... 

Investigations of magnetic field effects in radiation-chemical reactions belong to a new research area [1-3] called, for short, spin chemistry . For the last 15 years, both the magnetic field effects in radiolysis [4-7] and the related highly sensitive methods such as optically/fluorescent detected ESR (OD/FD ESR) [7-10] have been a subject of extensive reviews. 

Piland GB, Burdett JJ, Kurunthu D, Bardeen CJ (2013) Magnetic field effects on singlet fission and fluorescence decay dsmamics in amorphous rubrene. J Phys Chem C 117 1224-1236... 

Saik, VO. and Lipsky, S., Magnetic field effects on recombinant fluorescence comparison of VUV and fast electron excitation, Chem. Phys. Lett., 264, 649, 1997. 

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