Optical detection of magnetic resonance

Optical detection of magnetic resonance (ODMR) was attempted for measurements of the pH effects on the triplet state of purine to investigate the protonation site of purine at low temperatures (78JA7131). The ODMR spectrum did not show the presence of more than one triplet state at liquid helium temperatures. Since the protonated tautomers 1H,9H (3a) and H,1H (3b) have similar bond structures, their triplets should have similar zero-field parameters and are thus not easy to distinguish by ODMR. 

Luk KFS, Maki AH, Hoover RJ (1975) Studies of heavy metal binding with polynucleotides using optical detection of magnetic resonance. Silver binding. J Am Chem Soc 97 1241-1242... 

K. W. Rousslang, Optical detection of magnetic resonance in aromatic amino acids and proteins, Dissertation, University of Washington, Seattle, Washington (1976). 

A. L. Kwiram, Optical detection of magnetic resonance in molecular triplet states, in MTP International Review of Science, Ser. 1, Physical Chemistry 4 (C. A. McDowell, ed.), pp. 271-315, University Park Press, Baltimore (1972). 

A. L. Kwiram and J. B. A. Ross, Optical detection of magnetic resonance in biologically important molecules, Anna. Rev. Biophys. Bioeng. 11, 223-249 (1982). 

This mechanism leads to a highly spin-polarized triplet state with a characteristic intensity pattern in the EPR spectrum, which is observed by time-resolved techniques (either transient or pulse EPR). The zero field splitting (ZFS) of the triplet state, which dominates the EPR spectrum, is an important additional spectroscopic probe. It can also be determined by optical detection of magnetic resonance (ODMR), for a review of the techniques involved and applications see reference 15. These methods also yield information about dynamical aspects related to the formation, selective population and decay of the triplet states. The application of EPR and related techniques to triplet states in photosynthesis have been reviewed by several authors in the past15 22-100 102. The field was also thoroughly reviewed by Mobius103 and Weber45 in this series. 

Historically this field is an extension of the optical detection of magnetic resonance transitions of... 

Wrachtrup J, von Borczyskowski C, Bernard J, Orrit M and Brown R 1993 Optical detection of magnetic resonance in... 

UV spectra were obtained with a Varian spectrometer (Cary 15 and 17). Fluorescence, phosphorescence spectra, and the zero-field splitting parameters D and E of the triplet state were determined at 1.3K with an apparatus (31) for optical detection of magnetic resonance (ODMR) which was similar to the one described by Zuclich et al. (32). 

The differences in the population and depopulation rate constants and the phosphorescence probabilities of the three components of the triplet states form the basis of all the methods for Optical Detection of Magnetic Resonance in triplet states of jr-electron systems. These methods were developed after the discovery of optical spin polarisation and extended to inorganic solids. The essential physical difference from the optical double resonance in atoms developed by Alfred Kastler is to be found in the selection mechanism in optical double resonance, the polarisation of the resonant UV light, i.e. the symmetry of an applied field, is responsible for the selection. In optical spin polarisation, the selection is due to the spin-orbit coupling, and thus to an internal field. 

To our knowledge the first appheation of ODMR to a molecule of biological importance was made by Kwiram who in 1970 reported the optical detection of magnetic resonance signals from the tryptophan moiety of lysozyme. A more recent report dealt with frozen glassy solutions of tryptophan, tyrosine, and the protein, bovine serum albumin (BSA) loob) See Fig. 10. Discrepancies between the lifetimes involved in the phosphorescence decay and the fast-passage ODMR responses... 

There are a variety of techniques for the determination of the various parameters of the spin-Hamiltonian. Often applied are Electron Paramagnetic or Spin Resonance (EPR, ESR), Electron Nuclear Double Resonance (ENDOR), Electron Electron Double Resonance (ELDOR), Nuclear Magnetic Resonance (NMR), occassionally utilizing effects of Chemically Induced Dynamic Nuclear Polarization (CIDNP), Optical Detection of Magnetic Resonance (ODMR), Atomic Beam Spectroscopy and Optical Spectroscopy. The extraction of the magnetic parameters from the spectra obtained by application of these and related techniques follows procedures which may in detail depend on the technique, the state of the sample (gaseous, liquid, unordered solid, ordered solid) and on spectral resolution. For particulars, the reader is referred to the general references (D). 

Remarkably, laser-microwave DR spectroscopy was also applied to large biomolecules. The investigations concentrated on the electronic structure and excited state dynamics of fluorescent organic systems via optical detection of magnetic resonance in the triplet state. Plenty of work was also performed utilizing classical light sources (see, e.g.. Ref. 167). 

J. Wrachtrup, C. von Borczyskowski, J. Bernard, M. Orrit, R. Brown, Optical detection of magnetic resonance in single molecule. Letters to Nature 363 (1993) 244. 

If the separation among the sublevels is in the range of microwave frequency, sublevel properties can be obtained by observing the effect of microwave resonance on the emission from this state. The zero-field splitting is of the order of microwave frequency for most of rr/r states. Thus, the sublevel properties can be obtained by analyzing the effect of microwave resonance on the phosphorescence intensity. The method is called phosphorescence-microwave double resonance (PMDR) or optical detection of magnetic resonance (ODMR). 

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