$M$-shell x-ray-production cross sections in thin targets of ${}_{79}{}^{}{}_{}{}^{}\mathrm{Au}$, ${}_{82}{}^{}{}_{}{}^{}\mathrm{Pb}$, ${}_{83}{}^{}{}_{}{}^{}\mathrm{Bi}$, and ${}_{92}{}^{}{}_{}{}^{}\mathrm{U}$ by 0.3—2.6-MeV ${}_1{}^1{}_{}{}^{}\mathrm{H}_{}^{+}{}_{}{}^{}$ and ${}_2{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions

$M$-shell x-ray-production cross sections are reported for ${}_1{}^1{}_{}{}^{}\mathrm{H}_{}^{+}{}_{}{}^{}$ and ${}_2{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions incident on thin targets of ${}_{79}{}^{}{}_{}{}^{}\mathrm{Au}$, ${}_{82}{}^{}{}_{}{}^{}\mathrm{Pb}$, ${}_{83}{}^{}{}_{}{}^{}\mathrm{Bi}$, and ${}_{92}{}^{}{}_{}{}^{}\mathrm{U}$. The energy of the ions ranged from 0.3 to 2.6 MeV in increments of 0.1 MeV. The first Born calculations overpredict the data at all energies studied. The perturbed-stationary-state calculations with energy loss, Coulomb deflection, and relativistic effects agree with the present data for both ${}_1{}^1{}_{}{}^{}\mathrm{H}_{}^{+}{}_{}{}^{}$ and ${}_2{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ ions at ∼0.35 MeV/u, overpredict the data at higher $\frac{E_1}{A_1}$, and underpredict the data at lower $\frac{E_1}{A_1}$. The electron-capture contribution to the target ionization is calculated to be less than 3.4% for the targets, projectiles, and energies reported in this work.