ESR of Gamma Irradiated C2H204.2H2O Single Crystal

ARI - An International Journal for Physical and Engineering Sciences, 1998

Gamma-irradiation damage centres in [(CH) NH] CdCl single crystals have been investigated at room and liquid nitrogen temperatures by electron paramagnetic resonance (EPR) technique. It has been found that the gamma irradiation produces (CH) N> radical with A&"28.5, A, VV "28.6, A, WW "8.4, A, XX "15.1 G and g VV "2.0043, g WW "2.0065, g XX "2.0054 EPR parameters in the sample. The behaviour of the radical movement in the [(CH) NH] CdCl matrix is discussed in terms of the parameters obtained by analysing the data. No significant changes are observed in the EPR spectra in the temperature range from room to liquid nitrogen.

Ari - An International Journal for Physical and Engineering Sciences, 1998

The Journal of Physical Chemistry A, 1997

Single crystals of the amino acid analogue hippuric acid, PhCONHCH 2 COOH, have been X-irradiated at 295 K and studied using X-band EPR, ENDOR, and ENDOR-induced EPR (EIE) spectroscopy at 295 and 130 K. Two different radical species were observed and characterized. The dominant species is radical R1, PhCONH-• CH 2 , supposedly formed by net decarboxylation from a pristine oxidation product. The nitrogen hyperfine and quadrupolar interactions yield information on the electronic structure in the nitrogen valence orbitals. The second radical species, radical R2, is formed by a net hydrogen addition to the phenyl entity of hippuric acid. As a reduction product, it may be formed by protonation of the negatively charged anion of the phenyl group, but the alternative mechanism of direct hydrogen addition to the phenyl ring cannot be ruled out. Spectral simulations indicate that radical R1 contributes about 85% of the total EPR spectrum, while the remaining 15% is contributed by radical R2.

The Journal of Physical Chemistry A, 1997

Single crystals of room temperature γ-irradiated glycine have been studied with electron nuclear double resonance (ENDOR) and X-band and high-frequency continuous wave electron paramagnetic resonance (EPR) spectroscopies and electron spin echo spectroscopy. EchoEPR spectroscopy was used to distinguish the radicals with different phase memory relaxation times. Three radicals have been detected, which have been identified as NH 3 + -CH-COO -(radical A), CH 2 -COO -(radical B), and CH 2 -NH 2 (radical C). Whereas radicals A and B had been observed by other authors in the past, radical C was not detected previously. The hyperfine tensors of the two CH 2 protons and of one of the NH 2 protons were determined by ENDOR. ESEEM (electron spin echo envelope modulation) and HYSCORE (hyperfine sublevel correlation spectroscopy) experiments were performed in order to obtain the relative signs of the hyperfine coupling constants of the three protons.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011

a b s t r a c t l-Arginine hydrochloride monohydrate and l-arginine hydrobromide monohydrate single crystals are irradiated by 100 MeV Ag 8+ swift heavy ions. The residual gases liberated from the irradiated samples are monitored as a function of ion fluence using quadrupole mass analyzer. The C 2 H 3 + , C 2 H 2 , N 2 , CO, HCl and CO 2 are the dominant gases liberated. Fourier transform infrared spectra of irradiated crystals explain the breaking of bonds in a localized region of the crystals. The crystallinity of irradiated crystals is analyzed by powder X-ray diffractions.

2007

Single crystals of 2-thiothymine (5-methyl-2-thiouracil) have been γ-irradiated at 300 K and studied using EPR spectroscopy. The 5-thymil (5-yl) radical, formed by a net hydrogen-atom addition to the C(6) of 2-thiothymine base, has been studied in detail. The hyperfine tensors of methyl and methylene proton couplings are given together with the g-tensor. It has been shown that the calculated hyperfine proton couplings and relative orientation of the coupling tensors along the pyrimidine ring are similar to those observed earlier in 5-yl radicals in the single crystals of thymine and its derivatives. Although no large differences in the hyperfine couplings were found, calculated values of the g-tensor are appreciably larger in comparison to the other thymine-like systems, what is expected due to the presence of sulfur at C(2) in 2-thiothymine.

Radiation Physics and Chemistry, 1999

EPR spectra of gamma irradiated arsanilic acid single crystal shows rarely observed and unstable arsenate centred [(OH) 2 As=O] Á radical. There are two magnetically distinct sites in monoclinic lattice. The principal hyper®ne and g values of both sites are determined from spectra taking the large hyper®ne eects into account. The principal hyper®ne values are found to be A x =602, A y =437 and A z =428 Gauss for one site and A x =602, A y =438 and A z =429 Gauss for the other site. The g values of both sites are the same with the values g x =2.048, g y =2.001 and g=2.000. The radical is in slightly distorted C 3v symmetry. The unpaired electron is mainly localised on s orbitals of O atoms and partly on p orbital of central As atom. Calculations of EPR parameters for large hyper®ne values are discussed and some easily applicable numerical techniques are utilised.

Journal of Magnetic Resonance (1969), 1983

Radiation Physics and Chemistry, 1999

As shown from the crystal structure, the oxygen atom of Ph 3 P1CH0C(O)CH 3 forms both intra and intermolecular hydrogen bonds. X-irradiation of this compounds produces a room-temperature-stable radical which was studied by single crystal EPR/ENDOR spectroscopy. Comparison of the experimental hyper®ne couplings with those obtained from ab initio calculations shows that the radical cation Ph 3 P + 0CH1C(OH)CH 2 is formed under radiolysis. The principal directions of the hyper®ne tensors indicate that, in this process, some of the hydrogen bonds are broken and that the radical undergoes a drastic reorientation around the Ph 3 P0C bond.

Journal of Magnetic Resonance (1969), 1981

A room-temperature, -y-irradiated, single crystal of KH glutarate, presents an EPR spectrum which is the superposition of the spectrum of the -OOC-CH,-CH,-CH-COO-radical formed by hydrogen atom abstraction from a -CH, group and of the spectrum of a second radical which is stable for months at room temperature. An ENDOR investigation of the latter radical shows that it has an allyl-type structure -OOC-CH-CH-CH-COO-and occupies a position in the crystal lattice very close to that previously occupied by an undamaged molecule. Moreover, the analysis of the ENDOR lines attributable to the weakly coupled protons shows that the radical is bonded in the crystal lattice by hydrogen bonds with undamaged glutarate residues. The hyperfine coupling of the hydrogen-bonded proton is briefly discussed.