Relaxation Time Measurements by Longitudinally Modulated ENDOR Spectroscopy on Irradiated L-Alanine Single Crystal

Angelone, Rocco; Forte, Claudia; Pinzino, Calogero

doi:10.1006/jmra.1993.1002

Cited by 19 publications

(16 citation statements)

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“…On the other hand, Angelone et al [8] have found a longitudinal relaxation time of about 100 us from their variable frequency LOMENDOR data. Their experiment consists of irradiating the sample with an MW and two radiofrequency waves.…”

Section: Discussionmentioning

confidence: 96%

“…A different value of the spin-lattice relaxation time of SAR was obtained by using the LOMENDOR (Longitudinally Modulated ENDOR) technique by Angelone et al [8]. The w.;~l value determined at room temperature by these authors was of about 100 us, Recently Nakagawa et al measured the relaxation rate of SAR in samples irradiated with different doses by the pulsed ESR technique saturation recovery [9].…”

Section: Introductionmentioning

confidence: 98%

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Electron spin-lattice relaxation time and spectral diffusion in γ-irradiated l-alanine

Brustolon

Segre

1994

Appl. Magn. Reson.

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Abstract. We performed continuous (CW) wave and pulsed ESR experiments to obtain information on the relaxation behavior of the I-alanine radical in an irradiated single crystal. The analysis of the CW saturation behavior gives a relaxation time of 2.8 us, The echo detected saturation recovery was obtained for a number of different experimental conditions. In any case only a portion of the 120 G wide ESR spectrum can be affected by the microwave (MW) pulses, spectral diffusion is active and a multi-exponential decay is therefore obtained. We measured characteristic spectral diffusion times of 1 -10 and 20-50 us, We found that a long time of about 200 ).Is can be measured only by using a train of long selective saturating pulses and short detecting pulses. The stimulated echo decay is bi-exponential, and the characteristic times are very short. A variable temperature investigation in the range 200 to 290 K showed that the decay is governed by the spectral diffusion and by the transverse nuclear spin relaxation time T 2n of the methyl protons.

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%

Electron spin-lattice relaxation time and spectral diffusion in γ-irradiated l-alanine

Brustolon

Segre

1994

Appl. Magn. Reson.

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“…In order to describe tunneling effects one can expand the spectral density simply by adding L(ω) terms from Eq. [7]. The same expanded spectral density can be introduced in Eq.…”

Section: Figmentioning

confidence: 91%

“…A detailed microscopic picture of the origin of various relaxation mechanisms cannot be easily reconstructed due to significant disagreement in the experimental values of the measured parameters such as electron spin-lattice relaxation time, T 1 , or rotational correlation time, τ = τ ∞ exp( E/kT ) of the CH 3 group. For example, it can be demonstrated (10) that literature data for the CH 3 dynamics of the SAR1 center (1,4,5,7,12) differ in activation energy, E/k, from 1100 to 2100 K and even more for the preexponential factor, τ ∞ , from 0.1 to 0.001 ps. On the other hand, several characteristic relaxation times were measured and origins of the corresponding relaxation mechanisms are not completely clear (8,9).…”

Section: Introductionmentioning

confidence: 97%

A Pulse EPR Study of Longitudinal Relaxation of the Stable Radical in γ-Irradiated L-Alanine

Rakvin

Maltar-Strmečki

Cevc

et al. 2001

Journal of Magnetic Resonance

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“…T~e equilibrates levels that differ only in M s. T~n equilibrates levels that differ only in M v Tx~ is the cross relaxation process with AMs + AM~ = 0 (AM s = + 1, AM~ = u 1). T~2 (AM~ + AM~ = +2) was assumed to be significantly longer than Tx~ [23] and was not included in the model. Additional levels are connected to levels 1-4 ( Fig.…”

Section: Experimental Methods and Data Analysismentioning

confidence: 99%

Electron spin relaxation of radicals in γ-irradiated malonic acid and methyl malonic acid

Harbridge

2003

Appl. Magn. Reson.

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Radicals genemted by y-irradiation of malonic acid and methyl malonic acid were studied asa function of temperature by inversion recovery, echo-detected saturation recovery and electronelectron double resonance (ELDOR) at X-band, and by continuous-wave saturation recovery at Xband and S-band. ELDOR reductions for malonic acid radical in polycrystalline and single-crystal samples indicate that nuclear spin relaxation is faster than both electron spin relaxation and cross relaxation between 93 and 233 K. Deuteration of the carboxylate protons caused the maximum ELDOR reduction to shift from about 110 to 150 K, consistent with the assignment of the rapid nuclear spin relaxation to hydrogen-bonded proton dynamies. ELDOR enhancements for both radicals formed in methyl malonic acid indicate that cross relaxation is faster than both electron spin relaxation and nuclear spin relaxation between 77 and 220 K. Enhanced cross relaxation and electron spin relaxation ate attributed to the rotation of methyl groups at a rate comparable to the electron Larmor frequency. The temperature dependence of the enhancement of 1/T~, was analyzed to determine the activation energies for methyl rotation. The same radical is formed in irradiated methyl malonic acid and L-alanine, but the barrier to rotation of the ct-methyl is 500 K in the methyl malonic acid host and 1500 K in the L-alanine host, which indicates a large impact of the lattice on the barrier to rotation.

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Relaxation Time Measurements by Longitudinally Modulated ENDOR Spectroscopy on Irradiated L-Alanine Single Crystal

Cited by 19 publications

References 0 publications

Electron spin-lattice relaxation time and spectral diffusion in γ-irradiated l-alanine

Electron spin-lattice relaxation time and spectral diffusion in γ-irradiated l-alanine

A Pulse EPR Study of Longitudinal Relaxation of the Stable Radical in γ-Irradiated L-Alanine

Electron spin relaxation of radicals in γ-irradiated malonic acid and methyl malonic acid

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