W band

Prisner T F, van der Est A, BittI R, Lubitz W, Stehlik D and Mdbius K 1995 Time-resolved W-band (95 GHz) EPR spectroscopy of Zn-substituted reaction centers of Rhodobacter sphaeroides R-26 Chem. Phys. 194 361-70... 

W. Band and G.E. Duvall, Physical Nature of Shock Propagation, Amer. J. Phys. 29, 780(1961). 

D. ter Haar, Elements of Statistical Mechanics, Holt, Rinehart, and Winston, New York, 1954 W. Band, Introduction to Quantum Statistics, D. Van Nostrand Co., Inc., Princeton, N.J., 1955. 

The -tensor anisotropy of the quinone radical-anions is much larger than that of P+ or BChl a +. It can thus often be fully resolved at W-band or even at Q-band frequencies when deuterated samples are employed. An overview of the measured 0-tensor components has already been given by Weber45, and an interpretation of 0-tensors and their usefulness can be found in ref. 131. Significant progress in the calculation of g values of quinone radical-anions has been made, see references 134-139. 

The excellent resolution of the 0-tensor components at W band has been used to measure the relaxation properties of QA in the Zn-substituted bRC of R. sphaeroides.m The experiment showed, in contrast to the respective ubiquinone radical in organic solution, an anisotropic relaxation behavior in the pulse high field ESE experiments. From the analysis of the T2 experiments a motional anisotropy of Q% in the protein pocket was deduced with a preferred libration about the C-O symmetry axis. Recently, similar experiments were also performed on Qb- in ZnbRCs. Compared to QA different echo decay time constants were found. A model was proposed in which the relaxation is related to reorientational fluctuations around the quinones specific H-bonds to the protein.142... 

The first detection of the RP state in PS I single crystals was reported by Kamlowski et al.2il using transient EPR at X-band. Berthold et al.2 3 oriented PS I RCs in the B0 field of the W-band spectrometer. From the analysis of the polarization pattern they reproduced the RP geometry obtained in the single crystal data. High field EPR studies proved to be very useful as shown by Stehlik and coworkers who first used K-band EPR144,284, later the work was extended to a multifrequency approach including W-band by van der Est et al.285 and Zech et al.192. In the latter paper a complete analysis of the structure of the RP P 7o0 A -... 

Fuhs et al.m investigated P p0 Aj in multilayers of Synechocystis PCC 6803 oriented on mylar sheets by transient W-band EPR. They could show an enhanced resolution of structural parameters of the RP in this model system. A problem is the uncertainty of the orientation distribution (width 30 10°). Limitations and possibilities of the method are discussed in this work. The technique is interesting for all systems for which no single crystals are available. 

Single crystals of cubic boron nitride, with excess boron, have been studied20 by X-band and W-band EPR. Two types of defect were detected called D1 and D2. The D1 centre exhibits local axial < 111 > symmetry and ground spin state S = 1/2, with g = 2.0033 and gL = 2.0094 at T = 10 K. A broad line from D2 was observed only at X-band at high temperature with g = 2.0084. It was attributed to transitions inside the excited levels of another boron related defect. 

The angle dependence of the spin soliton in randomly oriented ladder poly-diactylene has also been investigated79 by pulsed HFEPR at 94 GHz. The shape of the 0-anisotropy-resolved nutation spectrum was discussed on the basis of the EPR transition moments and the differences between spin relaxation times. Reliable assignments of hyperfine couplings to the p-protons (P-H) of the alkyl side chains were achieved with the support of W-band ENDOR measurements. No significant orientational dependence of the 7i and Ti processes was found in terms of the isotropy of the p-H-hyperfine interaction. 

FIGURE 3.8 W-band EPR spectra of aligned single crystals of [Fe4(OCH3)6(dpm)6] at 5 K (only the S = 5 ground state is populated). Inset coupling scheme of the four Fe(III) (s = 5/2) centers. Additional smaller effects and structural isomers cause the spectrum to be more complex than anticipated.17... 

The most prominent feature in luminescence of Xe, Kr and Ar - the so-called M-band (Fig.la) - is formed by 1,3SU+— Xg+ transitions in (R2 ) excimer M-STE (R=rare gas atom). The negative electron affinity (Table 1) is a moving force of the cavity ("bubble") formation around A-STE in the bulk of crystal, and the desorption of atoms and excimers from the surface of solid Ne and Ar [11], Radiative "hot" transitions in desorbed excimers of Ar and Ne result in a W-band. 4-bands are emitted by A-STE (R ). 

Direct verification of DR-mechanism of DIET was provided [21] by combining the state-selective photoexcitation of the sample and the controlled thermally induced release of electrons from electron traps (Fig.9a). In RGS, after electron-hole pair creation at selective excitation by photons with energies E>Eg, the hole may survive and be self-trapped if the electron is captured by any kind of traps [32], In solid Ar at T>2 K the main part of electron traps is not active [12], the electron-hole recombination occurs before self-trapping the holes, and, therefore, the concentration of W-band emitting centers decreases (Fig.9a). On the contrary, the heating... 

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