Madison Ls 



Bighorn Dol 



Gallatin Ls. 



Temperature — °C 

 Figure 10-4. Typical glow curves for section 

 in Wind River mountains, Wyoming. 



thermoluminescence peaks at lower temperatures. Traces of impurities are 

 probably a factor in the thermoluminescence although the glow curve for sodium 

 chloride, for example, seems to be about the same for most samples, whether they 

 are taken from reagent bottles of different companies, from highly purified lab- 

 oratory preparations, or from deposits of rock salt; but they are greatly affected 

 by added impurities of certain ions. 



Many of the colorless oxides give thermoluminescence after exposure to 

 gamma rays. The colored oxides are probably so opaque that even if electrons 

 are trapped after exposure to gamma rays and liberated later by heating, the 

 thermoluminescence light is absorbed in the opaque outer layers so that it can- 

 not be observed with the eye or with a photomultiplier. Aluminum oxides have 



187 



