钽和铌在高温时会熔解入微量的氮气，这些氮气位于晶体的空位，它会影响钽和铌的物理、机械和化学性质。很难用一般方法测定难熔金属中的微量气体。

带电粒子及光子活化分析都可测定金属中的氮含量。常用的核反应及可能的干扰反应列于表1。前面四种核反应都已被广泛应用。由于它们产生的都是半衰期较短的纯

β

+

辐射体，所以，仅靠选择适当的入射粒子能量，有时干扰核反应仍很难避免。K. Strijckmans等

[1]

根据第五种核反应，用12MeV质子束测定难熔金属中的氮气，灵敏度可达0.4～0.3

µ

g•g

-1

。V. Vandecasteele等

[2]

用同样的核反应测定了铝-钛合金中的氮气。

Nitrogen was determined in Ta and Nb with charged particle Activation Analysis. The

14

O activity from the reaction

14

N (

p

n

)

14

O is produced by a beam of protons of 7.0 MeV. After chemical etching

the

14

O activity (Eγ=2.313 MeV) of the sample was measured by means of a Ge(Li) or NaI(T1) detector. The half-life of

14

O is 70.5sec. The analysis is nondestructive

and interferences do not arise. This method gives sensitivities of 0.5 and 6

µ

g · g

-1

for the analysis of Ta and Nb

respectively. Each analysis lasts about 5min. The method is applicable to determine trace nitrogen without chemical separation.