Summary
The lineshapes of the absorption bands ofF A centres in alkali halides have been studied for the first time. The new method used for this investigation is based on the determination of the overlap between theF A1 andF A2 bands from luminescence measurements. The experimental results have been compared with calculated values deduced from the theoreticalF A bands of different shapes. For bothF A (I) centres in KCl: Na+ andF A (II) centres in KCl: Li+ and RbCl: Li+ the absorption lineshape at low temperature is much closer to a sum of two Lorentzian curves than that of two Gaussian or Poissonian bands. This result shows an unexpected difference with theF centres, whose absorption lineshape is known to be Poissonian at the same temperatures.
Riassunto
Sono state studiate per la prima volta le forme di riga delle bande di assorbimento dei centriF A in alogenuri alcalini. Il nuovo metodo usato per questa indagine è basato sulla determinazione attraverso misure di luminescenza della sovrapposizione fra le bandeF A1 eF A2 . I risultati sperimentali sono stati confrontati con i valori dedotti da bandeF A teoriche di diverse forme. La forma di riga dell'assorbimento a bassa temperatura, sia per i centriF A (I) in KCl: Na+ sia per i centriF A (II) in KCl: Li+ e RbCl: Li+, è approssimata molto meglio da una somma di due curve Lorentziane che da quella di due bande Gaussiane o Poissoniane. Questo risultato rivela una differenza imprevista rispetto ai centriF, il cui assorbimento ha una forma di riga Poissoniana alle stesse temperature.
Резюме
Впервые исследуются формы линий зон поглощения дляF A центров в щелочно-галоидных соединениях. Предлагается новый метод исследования. Этот метод основан на определении перекрытия междуF A иF A2 зонами из измерений люминесценции. Экспериментальные результаты сравниваются с вычисленными величинами, полученными из теоретическихF A зон различной формы. ДляF A (I) центров в KCl: Na+ иF A (II) центров в KCl: Li+ и RbCl: Li+ форма линии поглощения при низких температурах оказывается ближе к сумме двух Лоренцевых кривых, а не двух Гауссовых или Пуассоновых зон. Этот результат обнаруживает неожиданное отличие отF центров, форма линии поглощения которых, как известно, представляет Пуассонову кривую при тех же температурах.
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Baldacchini, G., Giovenale, E., De Matteis, F. et al. Absorption lineshape ofF A centres in alkali halides. Il Nuovo Cimento D 10, 693–708 (1988). https://doi.org/10.1007/BF02451107
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DOI: https://doi.org/10.1007/BF02451107