We have applied the time-resolved and space-resolved spectroscopies of vapour zones produced by gradual thermal evaporation in a noble gas to study the electronic properties and stability of hydrogenated clusters and microcrystals. Optical extinction spectra of lithium vapour zones in pure Ar gas and Ar - H₂ gas mixture atmospheres confined at various pressures were obtained. Some comparisons of the observed spectra with those predicted theoretically indicate that hydrogenated clusters Li_nH_m are to be found near the vapour source, while lithium microcrystals coated with LiH shells are to be found far away from the vapour source. Electron localization around hydrogen atoms and the hydrogenation mechanism of lithium particles are also discussed.