Fluorescence detected magnetic resonance FDMR

Time-resolved laser flash ESR spectroscopy generates radicals with nonequilibrium spin populations and causes spectra with unusual signal directions and intensities. The signals may show absorption, emission, or both and be enhanced as much as 100-fold. Deviations from Boltzmann intensities, first noted in 1963, are known as chemically induced dynamic electron polarization (CIDEP). Because the splitting pattern of the intermediate remains unaffected, the CIDEP enhancement facilitates the detection of short-lived radicals. A related technique, fluorescence detected magnetic resonance (FDMR) offers improved time resolution and its sensitivity exceeds that of ESR. The FDMR experiment probes short-lived radical ion pairs, which form reaction products in electronically excited states that decay radiatively. ... 

A related technique, fluorescence detected magnetic resonance (FDMR), is suitable for the observation of short-lived radical ion pairs with lifetime in the range of... 

Detection using fluorescence-detected magnetic resonance (FDMR)... 

Two different types of pulsed EPR experiments are possible a spectrum can be measured at a fixed time after the pulse by variation of the field strength B (Eq. 72), or the time profile of a particular spectral line can be measured at constant B to give kinetic information. One vziriation of this kinetic method is to detect the recombination of singlet-state radical ion pairs in liquid hydrocarbons by the fluorescence of the product excited state [142]. This technique is known as fluorescence-detected magnetic resonance (FDMR) and provides information on the spin dynamics of the radical ion pair as well as the chemical kinetics. 

Psencik J, Searle GFW, Hala J and Schaafsma TJ (1994) Fluorescence-detected magnetic resonance (FDMR) of green sulfurphotosynthetic bacteria Chlorobium sp. Photosynth Res 40 1-10... 

Schmittel and Burghart have produced an excellent review, Understanding Reactivity Patterns of Radical Cations . The detection and observation of radical cations are highly desirable, but also have often been difficult, owing to their short lifetimes. West and Trifunac have developed a technique known as time-resolved fluorescence-detected magnetic resonance (FDMR) that gives the maximum possible time resolution for EPR and thus a window into fast radical cation reactions in solution. They have also linked this work with matrix isolation of radical cations using microporous zeolite reactors. 

Electron Spin Resonance Electron spin resonance measures the effect of micro-waves on a molecule with spin (usually a free radical or triplet) in a magnetic field. The detection can be either through the absorption of microwave energy (conventional ESR) or the effect of a microwave frequency on the emission of light (Fluorescence Detected Magnetic Resonance FDMR). Because the transition energy of the electron in a molecule depends on the interaction of that electron with much of the molecule, spectra have many lines and contain substantial information about the structure of the species being studied. 

Searle, G.F.W., Koehorst, R.B.M., Schaafsma, T.J., Miller, B.L., and von Wettstein, D. (1981). Fluorescence detected magnetic resonance (FDMR) spectroscopy of chlorophyll-proteins from barley, Carlsberg Res. Comm. 46, 183-194. 

This emission is assigned to fluorescence from the antenna-Bchl-b Sj-state. The fluorescence detected magnetic resonance (FDMR) spectrum given in fig. 2 was obtained in this emission band. (For a recent review on FDMR of bacterial photosynthesis see Hoff. 1982). From this spectrum d was calculated to be (160 + 2) x 10 cm , and e = (38 + 1) x 10 cm This is in good agreement with previously published results obtained with EPR-spectroscopy (Prince et al., 1976). 

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