Why freeze autorads?

Jonathan B. Marder MARDER at agri.huji.ac.il
Thu Nov 21 03:11:16 EST 1996


In article <57008p$1nem at news.doit.wisc.edu>, klenchin at facstaff.wisc.edu wrote:
>In article <3293A2DD.6BCF at pt.cyanamid.com>,
>   "S. Silverman" <silvermans at pt.cyanamid.com> wrote:
>->	The absorption and emission properties of the material in 
>->intensifying screens depend on temperature.  The screens are more 
>->efficient at low temp.  It will take someone with more familiarity with 
>->molecular orbital theory than me to give you a more precice reason.  
>
>I don't think so. Intensifying screens emit light upon absorption of
>high-energy particles. Light excites silver on film. Freezer is to 
>increase sensitivity of latter. 
>
>- Dima

The statement about temperature-sensitivity of the screens makes sense.
Certainly for fluorescence, yield usually goes up at low temperature.
This is because fluorescence competes with other deactivation processes 
which generally slow down at low temp. With a scintillant, the same should 
apply. The beta radiation excites the screen. If the excitation is lost
by non-radiative decay, then there is no emission. Low temperature should 
minimize this loss and increase the emission efficiency.



Jonathan B. Marder             ,      Department of Agricultural Botany
E-mail: MARDER at agri.huji.ac.il |      The Hebrew University of Jerusalem
Phone: (08 or +9728) 9481918   | /\/  Faculty of Agriculture
Fax:   (08 or +9728) 9467763   |/  \  P.O.Box 12, Rehovot 76100, ISRAEL
     http://www.agri.huji.ac.il/~marder



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