Spectral probes for the ${\mathrm{CH}}^{+}, {\mathrm{OH}}^{+}$, and ${\mathrm{SiH}}^{+}$ hydride molecular ions that play key roles in astrophysics and plasma processes are presented. The merged-beam technique at the SOLEIL synchrotron was used to record the photoionization (ion yield) spectra of ${\mathrm{CH}}^{+}, {\mathrm{OH}}^{+}$, and ${\mathrm{SiH}}^{+}$ and that of their parent atomic ions, in the $K$-shell and $L$-shell regions, respectively. Energies and oscillator strengths for the $K\alpha$ (${\mathrm{CH}}^{+}$ and ${\mathrm{OH}}^{+}$) and $L\alpha$ (${\mathrm{SiH}}^{+}$) transitions were determined from the spectra. Ab initio calculations interpret the experimental data in terms of contributions from ground and excited valence electronic states.

• Received 15 October 2015

DOI:https://doi.org/10.1103/PhysRevA.93.061401