Collisional quenching of 2 3P and 2 4P states in 33-MeV two- and three-electron Mg ions

The spectra of Mg Kα x rays, emitted in collisions of 33-MeV Mg ions with noble-gas atoms, have been measured using a curved-crystal spectrometer. Quenching of the metastable 1s2p 3P state of He-like Mg and the 1s2l2p 4P states of Li-like Mg caused the intensities of x rays from these states to decrease, relative to the intensities of x rays from the promptly decaying 1P and 2P states as the gas pressure increased. Quenching cross sections were determined by fitting the observed pressure dependence of the x-ray intensity ratios to a function derived from the rate equation for the production and decay of these states, with additional terms to account for contributions from prompt spectator-electron transitions. The quenching cross sections for the 3P state compare favorably with outer-shell electron-capture cross sections estimated from semiempirical scaling rules and recoil time-of-flight measurements