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Rakvin B, Carić D, Kveder M. Modulation sidebands spectra within inhomogeneous CW-EPR line detected by double modulation EPR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 307:106587. [PMID: 31499471 DOI: 10.1016/j.jmr.2019.106587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 08/26/2019] [Accepted: 08/28/2019] [Indexed: 06/10/2023]
Abstract
Conventional modulation spectrum, MS, in continuous wave electron paramagnetic resonance, CW-EPR, is produced by applying longitudinal radiofrequency (RF) fields with the frequencies, ωrf, which exceeds the linewidth, 2πδ, of a single spectral line given in frequency units. The second longitudinal RF field with frequency, ωrf2, is employed to produce double modulation spectrum, DMS. In this work DMS are presented as a specific type of MS which can be produced from an ordinary homogenous line. The numerical simulations of DMS in the limit of low power saturation relied on the recently introduced multi-photon transitions formalism which includes one microwave photon in combination with an arbitrary number of radiofrequency photons. It is shown that DMS of an inhomogeneous line exhibits similar basic structure as MS and exhibits sideband peaks at multiples of basic radiofrequencies. Linewidths of these peaks are significantly narrower (cca. two - three orders of magnitude) than the inhomogeneous linewidth and can be correlated with the underlying homogeneous linewidth components on the basis of characteristic spin-lattice, T1, and spin-spin, T2, relaxation times. The capability to extract T1 and T2 from DMS was tested on the well-known E' defect in irradiated vitreous SiO2. The obtained results revealed the impact of "rapid passage" effect on DMS in improving the detection sensitivity of DMS in the study of paramagnetic centers with long relaxation times. Therefore, double modulation method can be considered as a complementary method for studying inhomegeneous broadening in the EPR spectra.
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Affiliation(s)
- B Rakvin
- Ruđer Bošković Institute, Division of Physical Chemistry, Bijenička 54, Zagreb, Croatia.
| | - D Carić
- Ruđer Bošković Institute, Division of Physical Chemistry, Bijenička 54, Zagreb, Croatia
| | - M Kveder
- Ruđer Bošković Institute, Division of Physical Chemistry, Bijenička 54, Zagreb, Croatia
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Maltar-Strmečki N, Rakvin B. Investigation of the nitrogen hyperfine coupling of the second stable radical in γ-irradiated l-alanine crystals by 2D-HYSCORE spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 222:81-87. [PMID: 22854218 DOI: 10.1016/j.jmr.2012.06.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 06/28/2012] [Accepted: 06/30/2012] [Indexed: 06/01/2023]
Abstract
The second stable radical, NH(3)(+)C()(CH(3))COO(-), R2, in the γ-irradiated single crystal of l-alanine and its fully (15)N-enriched analogue were studied by an advanced pulsed EPR technique, 2D-HYSCORE (two-dimensional hyperfine sublevel correlation) spectroscopy at 200K. The nitrogen hyperfine coupling tensor of the R2 radical was determined from the HYSCORE data and provides new experimental data for improved characterization of the R2 radical in the crystal lattice. The results obtained complement the experimental proton data available for the R2 radical and could lead to increased accuracy and reliability of EPR spectrum simulations.
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Rakvin B, Maltar-Strmečki N, KattNig D, Grampp G. ENDOR study of the dynamic properties of stable paramagnetic centres in γ -irradiated L-alanine crystals. Mol Phys 2010. [DOI: 10.1080/00268970701616048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Rakvin B, Maltar-Strmečki N, Kattnig D, Grampp G. ENDOR Study on the Dynamic Properties of the First Stable Paramagnetic Center in γ-Irradiated l-Alanine Crystals. J Phys Chem A 2010; 114:7500-5. [DOI: 10.1021/jp103883x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Boris Rakvin
- Ruđer Bošković Institute, P.O. Box 180, 10002, Zagreb, Croatia, Faculty of Veterinary Medicine, University of Zagreb, P.O. Box 466, 10002, Zagreb, Croatia, and Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria
| | - Nadica Maltar-Strmečki
- Ruđer Bošković Institute, P.O. Box 180, 10002, Zagreb, Croatia, Faculty of Veterinary Medicine, University of Zagreb, P.O. Box 466, 10002, Zagreb, Croatia, and Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria
| | - Daniel Kattnig
- Ruđer Bošković Institute, P.O. Box 180, 10002, Zagreb, Croatia, Faculty of Veterinary Medicine, University of Zagreb, P.O. Box 466, 10002, Zagreb, Croatia, and Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria
| | - Günter Grampp
- Ruđer Bošković Institute, P.O. Box 180, 10002, Zagreb, Croatia, Faculty of Veterinary Medicine, University of Zagreb, P.O. Box 466, 10002, Zagreb, Croatia, and Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria
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Maltar-Strmecki N, Rakvin B. Evidence for disorder in L-alanine lattice detected by Pulsed-EPR spectroscopy at cryogenic temperatures. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2006; 63:784-7. [PMID: 16455297 DOI: 10.1016/j.saa.2005.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Revised: 09/23/2005] [Accepted: 10/01/2005] [Indexed: 05/06/2023]
Abstract
The unusual behavior of lattice dynamics of L-alanine has been assigned to intermolecular dynamics and localization of vibrational energy. Recent heat capacity and Pulsed-EPR measurements support presence of thermally activated dynamic orientational disorder in the L-alanine lattice below 20 K. In the present study, the additional evidence for possible thermally activated disordered behavior of L-alanine lattice have been obtained by investigating dependences of longitudinal relaxation time of first stable L-alanine radical, SAR1, on sample cooling rates for the same low temperature interval. The obtained relaxation time by Pulsed-EPR shows clear dependence on cooling rates and this behavior can be explained within two types of suggested spin-lattice relaxation mechanisms for the paramagnetic centers in the hydrogen-bonded organic crystal.
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Affiliation(s)
- N Maltar-Strmecki
- Faculty of Veterinary Medicine, University of Zagreb, P.O. Box 466, 10002 Zagreb, Croatia
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Rakvin B, Maltar-Strmečki N. Study of the first stable l-alanine paramagnetic center by 2D-HYSCORE spectroscopy: Detection of 14N hyperfine and quadrupole splitting. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.08.138] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Talbi S, Raffi J, Aréna S, Colombani J, Piccerelle P, Prinderre P, Dolo JM. EPR study of gamma induced radicals in amino acid powders. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2004; 60:1335-1341. [PMID: 15134732 DOI: 10.1016/j.saa.2003.10.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2003] [Accepted: 10/17/2003] [Indexed: 05/24/2023]
Abstract
To better understand the composite character of amino acids EPR spectra, the radiolysis and reactions which occurred after irradiation of amino acids, a comparative EPR study of a few simple amino acids has been made in order to identify qualitatively and quantitatively the different radiation-induced radicals in amino acid powders. A spin-trapping methodology has been developed and carried out on irradiated glycine, alanine and valine.
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Affiliation(s)
- S Talbi
- LRMO, case D52, UMR 6171, Faculté des Sciences de Saint-Jérôme, 13397 Marseille 20, France
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Rakvin B, Maltar-Strmecki N, Ramsey CM, Dalal NS. Heat capacity and electron spin echo evidence for low frequency vibrational modes and lattice disorder in L-alanine at cryogenic temperatures. J Chem Phys 2004; 120:6665-73. [PMID: 15267559 DOI: 10.1063/1.1666107] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
With the view of understanding the low frequency (40-50 cm(-1)) motional processes in L-alanine around 4 K, we have carried out heat capacity (CP) and electron spin echo (ESE) measurements on L-alanine and L-alanine-d7. The obtained CP data show the so-called boson peak (seen as a maximum in CP/T3 versus T plots) in the low temperature region (1.8-20 K). The phase memory time, T(M), and spin lattice relaxation time, T1, of the spin probe, the so-called first stable alanine radical (SAR1), *CHCH3COOH, have been measured between 4 and 105 K. The obtained relaxation rate 1/T1 shows an anomalous increase which coincides with the emergence of a boson peak in the low temperature region (4-20 K). Together, the ESE and the CP data confirm the existence of a thermally activated dynamic orientational disorder in the lattices of both compounds below 20 K. The results help explain the discrepancy between the CP data from powders and single crystals of alanine, as well as the proanomalous relaxation mechanisms for SAR1 in these lattices, and they also provide a mechanism for the spin-lattice relaxation process for SAR1 at cryogenic temperatures.
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Affiliation(s)
- B Rakvin
- Ruder Bosković Institute, P.O. Box 180, 10002, Zagreb, Croatia.
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Rakvin B, Maltar-Strmecki N, Cevc P, Arcon D. A pulse EPR study of longitudinal relaxation of the stable radical in gamma-irradiated L-alanine. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 152:149-155. [PMID: 11531373 DOI: 10.1006/jmre.2001.2373] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The longitudinal relaxation rate of the first stable alanine radical, SAR1, was studied by employing pulse EPR technique over a wide temperature interval (5-290 K). The complex nonexponential recovery of the longitudinal magnetization in this temperature interval has been described with two characteristic relaxation times, 1/T*(1a) as the faster component and 1/T*(1b) as the slower component, respectively. It was shown that 1/T*(1a) is strongly affected by the CH(3) group dynamics of the SAR1 center. The complete temperature dependence of 1/T*(1a) was described by invoking several relaxation mechanisms that involve hindered motion of the CH(3) group from classical rotational motion to coherent rotational tunneling. It was shown that all relevant relaxation mechanisms are determined by a single correlation time with the potential barrier (Delta E/k=1570 K). On the other hand the temperature dependence of 1/T*(1b) is related to the motional dynamics of the neighborly NH(3) and CH(3) groups. We found a larger average potential barrier for this motion (Delta E/k=2150 K) corresponding to smaller tunneling frequencies of the neighbor groups.
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Affiliation(s)
- B Rakvin
- Ruder Bosković Institute, 10002, Zagreb, Croatia.
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Vanhaelewyn GC, Amira SA, Mondelaers WK, Callens FJ. Decomposition study of the electron paramagnetic resonance spectrum of irradiated alanine. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2000; 56A:387-397. [PMID: 10727157 DOI: 10.1016/s1386-1425(99)00250-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Recent Electron Paramagnetic Resonance (EPR) studies on alanine powders as a function of irradiation dose and temperature on the one hand and single crystal Electron Nuclear DOuble Resonance (ENDOR) studies on the other hand, showed the presence of at least three radicals contributing to the total alanine EPR spectrum. The latter spectrum obtained after irradiation at room temperature (RT), is dominated by the well-known stable-alanine-radical (SAR) CH3C*HCOO-, also denoted R1. Appropriate heating of irradiated alanine causes the relative contribution of R1 to decrease, resulting in a spectrum mainly caused by the H-abstraction radical CH3C*(NH3)COO-, denoted R2. Although the EPR spectrum of these two radicals could be satisfactorily simulated, their influence on dose reconstruction has not been reported yet. Therefore, a detailed Maximum Likelihood Common Factor Analysis (MLCFA) study has been performed on EPR spectra from polycrystalline alanine samples, after irradiation and heat treatments. Conclusions concerning the number of contributing radicals and their influence on the RT irradiated alanine EPR spectrum will be made.
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Affiliation(s)
- G C Vanhaelewyn
- Laboratory for Crystallography and Study of the Solid State, University of Ghent, Gent, Belgium
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Rakvin B, Maltar-Strmecki N. Study of relaxation rates of stable paramagnetic centers in gamma-irradiated alanine. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2000; 56A:399-408. [PMID: 10727158 DOI: 10.1016/s1386-1425(99)00251-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The stable L-alanine radical induced by gamma-irradiation was examined by electron paramagnetic resonance (EPR), transfer saturation EPR and electron nuclear double resonance (ENDOR) in the temperature region of fast motion of the methyl group (180-320 K). From the obtained spectral line broadening and spectral intensity the correlation time for the methyl rotation was estimated. The complex processes determining the relaxation rate were examined in the same temperature interval. It was shown that important contributions to the relaxation rate arise from non-secular and pseudo-secular types of contributions. The non-secular contribution involves intramolecular dynamics while the pseudo-secular contribution originates from intermolecular motions. The obtained values for the dynamical parameters have been compared with those obtained by pulse EPR methods and by proton nuclear magnetic resonance (NMR) on undamaged crystals.
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Affiliation(s)
- B Rakvin
- Ruder Bosković Institute, Zagreb, Croatia.
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Cabral-Prieto A, Rubio J, Jiménez-Domı́nguez H. The resolution-enhanced ESR powder spectrum of γ-ray and UV-light irradiated unbound- and silicone-bound-alanine and its satellite lines. Appl Radiat Isot 1999. [DOI: 10.1016/s0969-8043(99)00103-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Lahorte P, Mondelaers W, De Frenne D, Callens F, Vanhaelewyn G, Schacht E, Van Calenberg S, Van Cleemput O, Huyghebaert A. Applied radiation research around a 15 MeV high-average-power linac. Radiat Phys Chem Oxf Engl 1993 1999. [DOI: 10.1016/s0969-806x(99)00226-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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