Am-241 X rays? -Reply

[FRAMEP@ORAU.GOV]

Gary Mansfield wrote in part:

>Some of our folks went to Lederer and Shirley, 1988 (Table of
>Isotopes) and came up with a total yield for the five L x rays of
>about 0.38.   Being a part-time internal dosimetrist, I reached for
>my trusty ICRP-38, which, if I punched the buttons on my calculator
>correctly, gives a value of about 0.64 for the total yield of these
>five L x rays.    hmmmm.  
>Looking a bit closer at the ICRP-38 data (to see if they perhaps
>threw in an extra x ray that no one else in the world had ever seen
>before) it appears as if their individual L x ray yields are all
>about 1.4 times the individual yields given by other references.   
>If anyone (Oak Ridge??) can shed some light (or maybe some x rays)
>on this

"If anyone (Oak Ridge??). ."   Man oh man, what a hook. I love it.
The temperature under a few collars must have jumped at that one.
Especially a few collars out Richland way :-)

The latest data I could pull from ORNL (updated last year) lists a
calculated value of 42 percent i.e. 0.42 and measured values between
37 and 45 percent i.e 0.37 to 0.45.

To me the problem seems to be with the ICRP data. One interesting
issue is that the latter lists three L conversion electrons (summed
intensity of 0.436) from transition 4 which has an energy of 32 keV.
According to the fluorescent yield, these electrons could lead to a
substantial production of L x-rays. Unfortunately, the ICRP doesn't
attribute x-rays to individual transitions which would help in
interpreting whats going on. Nevertheless, the other references I
have don't cite conversion electrons or x rays from this transition.
As would be expected, the ICRP summed intensity for L x-rays (0.639)
is the difference between the summed intensity for the L conversion
electrons (1.169) and the summed intensity for the L auger electrons
(0.534). All of these are higher than elsewhere, not just the x-ray
numbers.

There are other discrepancies with the ICRP data but this one seems 
particulary important (at first glance at any rate).  Perhaps the
current thinking is that transition 4 does not occur with the kind of
intensity assumed by the ICRP.

Thats my guess for what its worth.   

Fun stuff. Thanks for the neat question.

Paul Frame
Professional Training Programs
Oak Ridge Associated Universities
framep@orau.gov