Luminescence and resonant Raman scattering of color centers in irradiated crystalline L-alanine

Winkler, E.; Etchegoin, P.; Fainstein, A.; Fainstein, C.

doi:10.1103/physrevb.57.13477

Cited by 16 publications

(17 citation statements)

References 14 publications

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“…The increase in the SHG output at higher fluence implies that higher concentration of free radicals favours the movement of unpaired electrons along the radical sites, which increases the second-order polarizability of the molecular crystal. CH and NH 2 radicals produced after irradiation were trapped in the crystal lattice, and the concentration of free electron radicals is proportional to the radiation dose absorbed by the sample [13,14]. A similar observation has been reported for L-alanine and L-threonine single crystals [10,[15][16][17].…”

Section: Shg Measurementsupporting

confidence: 58%

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

Rao

Naseema

2010

Pramana - J Phys

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In this paper, we report the electron irradiation effects on the properties of an organic NLO single crystal of 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole. The crystal was irradiated with electron beam of different doses and was characterized by powder XRD, UV-Vis, FTIR, DSC, microhardness and SHG measurements. In XRD, the peaks are shifted due to irradiation. The SHG efficiency has been found to enhance rapidly with irradiation. The investigation of the influence of electron irradiation on the surface morphology of the grown crystal reveals the formation of craters on the surface. The laser damage threshold remains constant as the dose rate increases whereas refractive index increases after irradiation.

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Section: Shg Measurementsupporting

confidence: 58%

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

Rao

Naseema

2010

Pramana - J Phys

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“…For higher electron fluences, l max shifts well and the decrease in energy gap might be due to the increase in the conductivity due to the following reasons: (i) when high energy electron beam incident on the biomolecular solid like L-threonine, it undergoes a following chemical reaction CH 3 CHðOHÞCHðNH 3 Þ þ ðCOO À Þ À ! 6 MeV e À CH 3 CHCHðOHÞðCOOHÞ þ NH 2 (ii) Formation of CH and deaminated radicals ( NH 2 ) produced after irradiations were trapped in the crystal lattice and the concentration of free electron radicals is proportional to radiation dose absorbed by the sample [13]. Similar observation has been reported for L-alanine single crystals [14].…”

Section: Uv-vis-nir Spectral Measurementsmentioning

confidence: 63%

Investigations on the optical, thermal and surface modifications of electron irradiated l-threonine single crystals

Kumar¹,

Raj²,

Bogle³

et al. 2008

Applied Surface Science

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“…7 and we shall, in consequence, not dwell into the details. The full discussion of the mode labeling for the Raman modes of L-alanine can be found in several previous works on the subject.…”

Section: Raman Scattering and Luminescencementioning

confidence: 97%

“…Further details of the setup for the optical experiments have been given elsewhere. 7 As excitation for the RRS and PL experiments we used the nine Ar ϩ -laser lines, ranging from 514.5 to 454.5 nm, and a single mode polarized He-Ne laser ͑632.8 nm, 17 mW͒. As in Ref.…”

Section: Experimental Setup and Samplesmentioning

confidence: 99%

“…[3][4][5][6] We shall show how the optical techniques of RRS and PL can help adding evidence for the probable positions of the dopant and, finally, we shall make comparisons of the local defect introduced by Fe with a recently studied defect in L-alanine produced by electron bombardment at room temperature. 7 The paper is organized as follows. Section II describes the EPR and optical spectroscopy experimental setups as well as the samples used in this investigation.…”

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confidence: 99%

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Fe impurities inL-alanine: An EPR, luminescence, and Raman study

et al. 1999

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We present a study of low concentration Fe͑III͒ doping in crystalline L-alanine by means of electron paramagnetic resonance, resonant Raman scattering, and photoluminescence. The magnetic resonance experiments show that Fe͑III͒ occupies two inequivalent sites of rhombic symmetry in the L-alanine crystal. We obtain for the principal directions of the effective giromagnetic tensor the values g z ϭ1.881(5), g y ϭ4.641(8), and g x ϭ7.238(5). In the optical experiments we find a selective resonant enhancement of some of the Raman active lattice vibrations comprising displacements of the hydrogen bonds between the carboxyl and ammonium groups of neighboring molecules. Based on these results we discuss the possible localization of the impurity in the crystal. ͓S0163-1829͑99͒06401-2͔ I. MOTIVATIONOrganometallic compounds play an important role in the biological functions of organisms. In contrast to carbon, hydrogen, oxygen, and nitrogen, metals exist in rather tiny proportions in biomolecules. Their existence is, notwithstanding, essential for some of the most important functions that proteins undertake in living matter. 1 The reversible binding of molecular oxygen carried off by the prosthetic heme group in myoglobin and hemoglobin is one important example. In this latter example, iron ͑Fe͒ can be observed either as divalent ͑oxyhemoglobin͒ or trivalent ͑ferrihemoglo-bin͒ depending on the experimental conditions. Metals serve also as cofactors of many enzymes; most enzyme classes include metal-dependent enzymes. Metalproteins are complex examples of interactions between metals and aminoacids. Simpler prototypes can be obtained by metal containing polyaminoacids or metal-aminoacid crystals. Their physics is not directly applicable to the properties of proteins and enzymes but rather constitute important model examples where a better understanding of the interaction between metals and aminoacids can be foretold. The study of their magnetic and electronic properties strives to obtain valuable information on the behavior of these ions in biologically relevant macromolecules. Copper ͑Cu͒ has played an important role in the study of metal-aminoacid single crystals. 2 Cu-doped L-alanine crystals have been extensively studied by electron paramagnetic resonance ͑EPR͒ and electron-nuclear double resonance ͑ENDOR͒ spectroscopy, leading to a detailed description of the site occupied by the impurities and their interactions with the ligands. 3 On the other hand, though Fe is one of the most important transition metal ions in living organisms, Fe-doped aminoacid crystals have not been studied to the same extent. In fact, the crystal structure revealing the position of the Fe impurities and their interactions with the molecular field of the crystal have not been, to the best of our knowledge, heretofore clearly worked out. The reasons for this lack of experimental information may be threefold. First, Fe impurities are accepted in rather low concentrations in aminoacid single crystals and, in any case, the crystal growth process is fa...

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Luminescence and resonant Raman scattering of color centers in irradiated crystalline L-alanine

Cited by 16 publications

References 14 publications

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

Investigations on the optical, thermal and surface modifications of electron irradiated l-threonine single crystals

Fe impurities inL-alanine: An EPR, luminescence, and Raman study

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