Monatomic hydrogen

Tantalum. Above 300°C (570°F), the possibihty of reactivity of tantalum with all gases except the inert gases. Below 300°C (570°F), the possibility of embrittlement of tantalum by nascent (monatomic) hydrogen (but not molecular hydrogen). Nascent hydrogen is produced by galvanic action or as a product of corrosion by certain chemicals. 

Fig. 16. Infrared absorption spectra for boron-implanted silicon after passivation in either monatomic hydrogen or deuterium. The specimens were passivated at 150°C for 1 h (per surface), and the spectral resolution is 4 cm-. From Johnson (1985). 

REACTIONS CHANGING THE CHARGE STATE OF MONATOMIC HYDROGEN SPECIES... 

Another conceivable limiting case, though one less likely to be approached in practical cases, is that where the total hydrogen concentration always remains far below that of the traps, which continue to capture hydrogen irreversibly. For this case, as Corbett et al. (1986) have pointed out, the concentration of free monatomic hydrogen will approach a quasisteady-state profile that decays exponentially with the depth x. The concentration of trapped hydrogen, of course, will at any point of space approach a linear increase with time. 

Fig. 9. Typical profile of the distribution n0(x) of mobile H° (a convenient measure for the density of all monatomic hydrogen if H+ and/or H are equilibrated with H0) at an arbitrary time during an experiment on a slab-shaped crystal specimen. The surface boundary conditions at the entrance and exit surfaces are defined by the diffusion offset lenghts dem and, respectively.

See Bacher and Goudsmit1 for a discussion of the energy states of gaseous monatomic hydrogen. 

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