ORNL-4191 - the Molten Salt Energy Technologies Web Site

w
M O+
MoF +
II
145
...... ~ .......
I 1
MoFJ'
7 - 1 - - -
MoF.
MnDF2+ MoOFZ
MOF+ M"Oi+
MOO+
ORNL--DWG 67 -103403
r-
~
.J. ....
90 (00 110 120 ,130 140 150 160 170 180 490 XO
ornu
Fig. 11.1. Mass Spectra of Sample I1 (MoF3) During a Heating Cycle from 25OoC to 725°C.
the MoOF, '/MoF3+, MoOF, t/MoF4t, and MoF5'
peaks at 375°C is shown in Fig. 11.2. This shows,
for illustrative purposes, the combined spectra for
the various isotopes and compounds in the mass
range from 150 to 194 amu. At 725OC the peak
height for the MoF,+ relative to the height of the
Mop,' peaks as compared with the spectrum at
375O allowed calculation of a tentative cracking
patteni assigned to MoF,. This is seen only at
elevated temperatures. An impurity at m/e - 167
wiis assigned the probable fonnula Si 20F,.
Mass analysis of these species is facilitated by
the unique isotopic abundance ratios of molybdenum
isotopes and the difference of 3 amu between oxy-
gen and fluorine. This yields, if one selects ad-
jacent pairs of species from the Mo0,F2+/M~~OF3t/
MoF4+ family of peaks, three unique peaks for each
species, allowing a precise calculation of the peak
height ratios for the "overlapping" peaks to be
made. The dimer Mo,F, has, of course, the 15
peaks which would be expected from the seven
stable molybdenum isotopes. Figure 11.3 shows
the good agreement between the calculated and the
-- I - r
155 171 193
m/e
PHOTO 89172
Fig. 11.2. Oscilloscope Trace of Mass Spectrum of
Sample II (MoF3).