Pancake GM and NaI Efficiencies

[LRGreger@aol.com]

I'm attempting to determine approximate field contamination counting
efficiencies for commonly encountered radionuclides.  I've received some from
my equipment supplier (Ludlum), and have been able to approximate others from
their beta characteristics.  I've not been able to locate references on EC
nuclides, however, and was hoping that someone might be willing and able to
help out.  I've unsuccessfully attempted to search the radsafe archives for
the information.

The nuclides that I'm particularly interested in are: Co-57, Ga-67, Tc-99m,
In-111, I-123, and Tl-201.  The counting equipment of interest are a typical
1.5 to 2 mg/cm2 window pancake GM (e.g. Ludlum 44-9) and a 1 x 1 NaI (e.g.
Ludlum 44-2) and/or a 1/2 x 1 NaI (e.g. Ludlum 44-62).  

I realize that there are minor differences in survey equipment and surfaces,
as well as geometry,  that will affect the counting efficiencies; however, I'm
only interested in approximate efficiencies.
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