Effect of temperature on lyoluminescence of divalent impuriy doped sodium chloride

Abstract

<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:hiddenhorzocr;="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The effect <span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">of temperature on the lyoluminescence (LL) of divalent impurity doped sodium chloride has been reported. When the NaCl crystallites irradiated using ⁶⁰Co source are dissolved in distilled water, initially the LL intensity increases with time, attains a maximum value, then it decreases and finally disappears. The peak <i>l</i>_m<i>, </i>of LL intensity versus time curve initially increases with temperature, attains an optimum value at a particular temperature and then it decreases with further increase in temperature. However, the total intensity <i>I</i>_T and time <i>t</i>_m, corresponding to the peak of LL intensity versus time curves decrease with increasing temperature of the solution. The peak intensity <i>l</i>_m<i>, </i>is maximum at a particular temperature because of the competition between increase in rate of dissolution of NaCl with temperature and decrease in efficiency η and density of <i>F</i>-centres with temperature. The value of time <i>t</i>_m, decreases with increasing temperature of the solution because of the increasing rate constant for the recombination of hydrated electrons with holes. The efficiency η and <i>n</i>_F decrease with temperature and therefore, the total intensity <i>I</i>_T decreases with increasing temperature of the solution. The decay time τ depends inversely on the rate of dissolution α, of solute in the solvent. Since α increases with increasing temperature of the solution, τ decreases with increasing temperature of the solution.</span></span>