Re: Luminescence & LSC

["Don_Jordan" <Don_Jordan@fpm.uchicago.edu>]

Chemiluminescence is indeed a single photon event, at least for each
molecule involved.  There are, however, lots of molecules in a 8-20 ml LSC
vial.  The coincidence counting techhnique employed in all LSC's since the
mid 50's can deal with low levels of chemiluminescence, but if the rate
gets very large, there will be a statistical chance that two single photons
from two seperate chemiluminescence events will be detected in each of the
photo tubes of the LSC.  Modern LSC's have random coincidence monitors that
can alert the user to the presence of chemiluminescence, and our Packard
counter will automatically correct for it.  

As Mr. Nabor states, chemiluminescence will all occur in the very lowest
channels of the H-3 window.  It can be be rejected by setting the lower
limit of your counting windows above zero.


Don

Don Jordan	
The University of Chicago	
Office of Radiation Safety
Zoology Building Room 11
1101 East 57th Street
Chicago,  Illinois  60637
Tel.	773-702-6299
Fax	773-702-4008
email Don_Jordan@fpm.uchicago.edu