Paramagnetic Resonance ofFCenters in Alkali Halides

Abstract

The F-center slow-and fast-passage electron spin resonance has been observed in LiF, LiCl, NaF, NaCl, NaBr, KC1, and KBr. The hyperfme coupling of the F electron to nuclei neighboring the negative-ion vacancy has been measured by electron-nuclear double resonance. Root second moments of the resonance absorption, obtained from slow passage, agree with values calculated from the hyperfme constants. In the case of LiF, the partially resolved structure existing on the slow passage resonance line is shown conclusively to arise from the F center. These experimental results, together with those of previous workers, are compared with the theory of Gourary and Adrian.

F centers in LiF: A nuclear magnetic resonance study

“…electrons at an empty anion site, are formed relatively easily. F centers in alkali halides have widely been studied over the last fifty years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] by optical absorption spectroscopy, nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and other techniques. As these studies have shown, the F center EPR spectra show orientation dependent hyperfine splittings due to the interaction with the neighboring lithium and fluorine atoms.…”

Wavefunction character of the F-center in table salt

“…The optical transition of the F-centers in alkaline metal halides occurs between the 1s state and the 2p states according to the dipole selection rule. The energy gap between the occupied 1s states and the unoccupied 2p states of the Fcenters in NaCl is calculated to be about 1.5 eV, which is lower than the experimental value (about 2.7 eV from the maximum absorption) [9,27]. The energy gaps of insulators/semiconductors are in general underestimated by the DFT-LDA method [24].…”

“…The dependences of the band gap and color center absorption on the cation are identical, reflecting the dominant role of the anions in both cases. Sodium shows a deviation, possibly due to the a-symmetrical shape of the peak of the color center [9,27].…”

New ultraviolet B emission from gadolinium activated BaZrO3 phosphor - An electron paramagnetic resonance and optical study

“…An unusually large linewidth is observed in alkali halides as the electron is delocalized and interacts with several alkali and halide ions from successive neighboring shells. In KCl, the observed line width is approximately 20 gauss [42] and in LiCl it is 58 gauss [42]. In other systems like HgI 2 .2HgS [43] and BaO [44], the linewidths are about 10 gauss and 3.5 gauss respectively.…”