What is meant by "forbiddenness of the decay path?"

["Jacobus, John (OD)" <JJacobus@exchange.nih.gov>]

I am reviewing a manual that discusses beta decay, which indicates that some
paths are forbidden?  Can anyone tell me that refers to?  Are there
probabilistic values associated with this?

-- John 

"It isn't necessary to imagine the world ending in fire or ice-there are two
other possibilities: one is paperwork, and the other is nostalgia." 
-Frank Zap 



John Jacobus, MS
Health Physicist
National Institutes of Health
Radiation Safety Branch, Building 21
21 Wilson Drive, MSC 6780
Bethesda, MD  20892-6780
Phone: 301-496-5774      Fax: 301-496-3544
jjacobus@exchange.nih.gov (W)
jenday@ix.netcom.com (H)
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