Naslov
Determination of the reaction dynamics of sodium hydride in a hydrogen atmosphere with degenerate four-wave mixing

Autori
Lehr, Leo ; Motzkus, Marcus ; Pichler, Goran ; Kompa, Karl Ludwig ; Hering, Peter

Izvornik
Journal of Raman spectroscopy (0377-0486) 29 (1998), 4; 273-282

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
NaH; DFWM; reaction dynamics; diffusion

Sažetak
Degenerate four-wave mixing was successfully applied to the determination of the reactive and diffusive loss mechanisms of photochemically produced sodium hydride in Na + H2 and Na + H2 + Ar atmospheres and in a supplement argon filling. Sodium hydride is formed on the microsecond time-scale in a quenching-reaction sequence after the 3s-3p excitation of sodium in the excitation volume. The concentration of NaH decreases with time depending on the buffer gas pressure. For small pressures (<20 hPa) diffusion out of the detection volume is the predominant process. The binary diffusion constant of sodium hydride in hydrogen was determined to be 0.66&#177; 0.07 cm2 s-1 at 1013 hPa and 273 K. Moreover, experimental data show an additional reactive loss mechanism present at high gas pressures. A second-order reaction with a thermal rate constant of k2=3.8×10-7 cm-3 s-1 (=5.6×10-12 cm2) at 520 K was observed. The thermal rate constant is independent of the hydrogen partial pressure, indicating that the reaction NaH + NaHNa2 + H2 is most probable. The activation energy of the reaction was estimated to be of the order of 0.9 eV.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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