Electron spin‐lattice relaxation times of transient free radicals

1981 ◽  
Vol 74 (7) ◽  
pp. 3694-3704 ◽  
Author(s):  
Richard W. Fessenden ◽  
Joseph P. Hornak ◽  
Balu Venkataraman
Keyword(s):  
Free Radicals ◽  
Electron Spin ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

94. Electron spin-lattice relaxation times

Physica ◽  
1958 ◽  
Vol 24 ◽  
pp. S163 ◽  
Author(s):  
M.W.P. Strandberg ◽  
C.F. Dams ◽  
R.L. Kyhl
Keyword(s):  
Electron Spin ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

scholarly journals Overhauser-Effekt und Relaxation in organischen Festkörperradikalen

1966 ◽  
Vol 21 (1-2) ◽  
pp. 158-164 ◽  
Author(s):  
J. Haupt ◽  
W. Müller-Warmuth
Keyword(s):  
Electron Spin ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Esr Spectra ◽  
Spin Lattice Relaxation ◽  
Electron Interaction ◽  
Proton Relaxation ◽  
Spin Lattice ◽  
Line Shapes ◽  
Random Character

The dynamic proton polarization, and the proton and electron spin relaxations have been studied in the organic polycrystalline free radicals bis-diphenylene-p-chlor-phenyl allyl (BPA), diphenyl picryl hydrazyl (DPPH), WURSTER'S blue perchlorate (WBP) and galvinoxyl (GAV). Enhancement factors between +370 and +79 were observed; extrapolation to infinite microwave power yielded values near the theoretical γs/γI ratio. Electron spin-lattice relaxation times are of the order of 10-7 to 10-8 sec; proton relaxation times are of the order of 10-3 sec. With the exception of galvinoxyl at low temperatures, the proton resonance line shapes are not much influenced by the local field of the unpaired electrons. The ESR spectra show a typical exchange-narrowing. All the results are discussed in terms of a scalar nuclear-electron interaction in which electron-electron exchange couplings provide a time dependence of random character.

Chlorine NQR Spin-Lattice Relaxation and Electron Spin Dynamics in Paramagnetic [Co(H2O)6[PtCl6]

1991 ◽  
Vol 46 (12) ◽  
pp. 1103-1107 ◽  
Author(s):  
Motohiro Mizuno ◽  
Tetsuo Asaji ◽  
Atsushi Tachikawa ◽  
Daiyu Nakamura
Keyword(s):  
Temperature Dependence ◽  
Electron Spin ◽  
Correlation Time ◽  
Spin Exchange ◽  
Energy Gap ◽  
Spin Dynamics ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Abstract Chlorine NQR spin-lattice relaxation times T1Q were determined for [Co(H2O)6][PtCl6] at 4.2 400 K. Above ca. 350 K, T1Q decreased rapidly showing the onset of a reorientation of [PtCl6]2-. The activation energy Ea of this reorientation was determined as 125 ± 15 kJ mol-1. With decreasing temperature, T1Q showed a maximum at ca. 250 K. Below ca. 200 K, T1Q. is governed by the magnetic dipolar interaction between chlorines and paramagnetic Co2+ ions and is inversely proportional to the electron spin correlation time τe of CO2+ . τe is shown to be determined by the electron spin-lattice relaxation time T1e and the temperature independent correlation time rs for the spin-exchange between neighbouring ions above and below ca. 50 K, respectively. The temperature dependence of T1e is explained by assuming the Orbach process with an energy gap A/k of 530 + 20 K as T1e = 5 x 10-14 exp(530/T)s. τs was estimated to be 0.9 x 10-10 s. The temperature dependence of the ESR linewidth of Mn2+ impurities in single crystal was also measured, intending to study Co2+ spin dynamics. The limit of the ESR method is discussed by comparing the obtained results with those of the NQR method

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