Molybdenum is a significant impurity in several high-purity materials such as special metals, e.g., niobium, hafnium, tantalum, rhenium and tungsten, and also sometimes -depending on the origin and preparation procedurein other metals such as iron, cobalt, copper, etc.
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There exist many chemical and physical methods for the determination of molybdenum which have been excellently compiled by Elwell and Wood [ 1 J .
Reviewing these methods one can see that, for different reasons, very few of them can detect molybdenum at the lower p.p.m. range and below in metallic matrices; the detection limit often depends very strongly on the matrix. For most of the above-mentioned metallic matrices, radiochemical neutron activation analysis is the most sensitive method, despite the fact that the crosssections of the principal reactions and/or the Y-ray intensities of the indicator radionuclides are rather low. The daughter technetium radionuclides 99mTc and iolTc formed by decay from the product radionuclides of the 'sMo(n,r) 99Mo and 'O'Mo(n,y) 'O*Mo reactions have often been detected. A detection limit down to about 0.1 p.p.m. can be achieved for the determination of molybdenum in difficult matrices [2-51.
However, neutron activation analysis is not very suitable for instrumental performance of the analysis. Even in matrices as suitable for instrumental neutron activation analysis as niobium and aluminium, experience has shown that molybdenum cannot be determined instrumentally at concentration levels much lower than 10 p.p.m. Recently, molybdenum was included in the instrumental multi-element proton activation analysis of tantalum [6] and niobium [7] . From these two applications it is evident that proton activation analysis is, generally, a very interesting technique for the determination of molybdenum.
In the work described here, the application of all relevant proton-induced reactions to the determination of molybdenum was systematically investigated at proton energies of 12 MeV and 16 MeV. The following reactions were studied: 92Mo(p,n)g2Tc, 94Mo(p,n)94gTc -+ gsMo(p,2n)94sTc, 9sMo(p,n)95mTc + 96Mo(p,2n)9smTc, 9SMo(p,n)gSeTc + 9GMo(p,2n)9sgTc, 96Mo(p,n)9GgTc + 97Mo(p,2n)96gTc and looMo(p,2n) 9gmTc. In addition to a high sensitivity, an