From: tenney@med.unc.edu (Charles R. Tenney)
Subject: Re: Cesium, of course.
Organization: UNC-CH School of Medicine
Date: Wed, 9 Sep 1992 23:06:03 GMT

In article <18k43tINNo73@agate.berkeley.edu> gezelter@sam.cchem.berkeley.edu (Dan Gezelter) writes:
>Cesium's  more interesting properties:
>                            -4
>% of earth's crust: 3.2 x 10
>                   
>Density: 1.873 g / cm^3
>Melting Point:  28.5 C
>Boiling Point:  705 C
>Sublimation energy (@ 25 C): 78.78 kJ/mol
>Ionization energies:  (in eV)
>   1st:  3.894
>   2nd:  25.1
>   3rd:  35
>Atomic radius: 263 pm
>Heat of hydration (from a gas): 264 kJ/mol
>
>Cesium can be obtained by reduction of Cs CO  with carbon or byh the 
>                                         2  3 
>thermal decomposition of cesium tartarate.
>
>              Cs CO  + 2C --->  2Cs + 3CO
>                2  3
>Cesium is used in photoelectric cells, since the absorption of radiant
>energy in the visible region of the spectrum can remove an electron
>because of its low ionization energy.  Cesium also serves as a
>"getter" in vacuum tubes, removing the last traces of corrosive gases
>in the tube when it is first put into use.
>

Cesium is also used in x-ray detectors, most notably in cesium iodide
image intensifier tubes.  You may, therefore, be interested in the fact
that it has a k-alpha x-ray energy of 30.851 keV and a k-beta energy of 35.131
keV (weighted averages).  The k-fluorescent yield is 0.895, and the probability
that any given k-fluorescent x-ray will be an alpha is 0.810.  Flourescent
x-rays are, of course, important to x-ray detection in their tendancy to
carry energy away from the site of initial interaction, depositing it
where it is not wanted, or perhaps losing it altogether if the fluorescent
photon escapes the detector.  You also may wish to peruse the following x-ray
interaction cross-sections, given in barns per atom.  Don't forget to
multiply by the conversion factor 0.004531 if you want mass attenuation
coefficients in cm**2/gm.  Energies are given in keV.  Note the change in
photoelectric effect at the absorption edges, for which there are two
lines of data at the same energy (just below and just above the edge).

ENERGY PHOTOELECTRIC COHERENT  INCOHERENT

1.0        2.05E+6   1.90E+3   1.34E+0
1.065      1.81E+6   1.89E+3   1.46E+0
1.065      1.92E+6   1.89E+3   1.46E+0
1.217      1.44E+6   1.85E+3   1.72E+0
1.217      1.50E+6   1.85E+3   1.72E+0
1.5        9.48E+5   1.79E+3   2.21E+0
2.0        4.78E+5   1.68E+3   3.11E+0
3.0        1.79E+5   1.46E+3   4.87E+0
4.0        8.59E+4   1.27E+3   6.50E+0
5.0        4.95E+4   1.11E+3   7.92E+0
5.012      4.92E+4   1.11E+3   7.93E+0
5.012      1.50E+5   1.11E+3   7.93E+0
5.360      1.24E+5   1.06E+3   8.38E+0
5.360      1.71E+5   1.06E+3   8.38E+0
5.713      1.45E+5   1.02E+3   8.81E+0
5.713      1.67E+5   1.02E+3   8.81E+0
6.0        1.47E+5   9.85E+2   9.15E+0
8.0        6.97E+4   7.84E+2   1.13E+1
10.0       3.86E+4   6.38E+2   1.31E+1
15.0       1.29E+4   4.19E+2   1.65E+1
20.0       5.84E+3   3.00E+2   1.89E+1
30.0       1.87E+3   1.72E+2   2.16E+1
35.985     1.14E+3   1.31E+2   2.26E+1
35.985     6.78E+3   1.31E+2   2.26E+1
40.0       5.13E+3   1.12E+2   2.31E+1
50.0       2.83E+3   7.89E+1   2.39E+1
60.0       1.73E+3   5.88E+1   2.43E+1
80.0       7.80E+2   3.57E+1   2.44E+1
100.0      4.16E+2   2.36E+1   2.41E+1
150.0      1.32E+2   1.11E+1   2.29E+1
200.0      5.81E+1   6.44E+0   2.14E+1

	     



>
>Back off, man.  I'm a chemist.

Consider me backed off.  I'm a medical physicist.

>_________________________________________________________________________
>Don't step on my blue suede .sig      gezelter@lithium.cchem.berkeley.edu
>-------------------------------------------------------------------------
-- 
--
Charles R. Tenney	tenney@med.unc.edu   | What would the UNC school of
					     | Medicine want with my opinions?
	"My karma ran over my dogma."	     | What would I want with theirs?
Newsgroups: alt.cesium