Hydrogen sulfide radicals in the ground state, SH(X), and hydrogen disulfide molecules, H₂S, are both detected in the interstellar medium, but the returned SH(X)/H₂S abundance ratios imply a depletion of the former relative to that predicted by current models (which assume that photon absorption by H₂S at energies below the ionization limit results in H + SH photoproducts). Here we report that translational spectroscopy measurements of the H atoms and S(¹D) atoms formed by photolysis of jet-cooled H₂S molecules at many wavelengths in the range 122 ≤ λ ≤155 nm offer a rationale for this apparent depletion; the quantum yield for forming SH(X) products, Γ, decreases from unity (at the longest excitation wavelengths) to zero at short wavelengths. Convoluting the wavelength dependences of Γ, the H₂S parent absorption and the interstellar radiation field implies that only ~26% of photoexcitation events result in SH(X) products. The findings suggest a need to revise the relevant astrochemical models.

在星际介质中都检测到了基态的硫化氢自由基SH（X）和二硫化氢分子H ₂ S，但是返回的SH（X）/ H ₂ S的丰度比意味着前一种相对的耗尽到当前模型所预测的结果（假定在低于电离极限的能量下，H ₂ S吸收光子会产生H + SH光产物）。这里，我们报告的H原子和S（那平移光谱测量¹通过射流冷却H的光解形成d）原子₂在许多波长范围为122≤小号分子 λ ≤155nm为这种明显的耗尽提供了理论依据；形成SH（X）产物Γ的量子产率从单位（在最长激发波长处）降低到在短波长处为零。对Γ的波长依赖性，H ₂ S母体吸收和星际辐射场进行卷积，表明只有约26％的光激发事件产生了SH（X）产物。研究结果表明有必要修改相关的地球化学模型。