Observation of charge-transfer population of high-<i>n</i>levels in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Ar</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>16</mml:mn><mml:mn/></mml:mrow></mml:msup></mml:mrow></mml:math>from neutral hydrogen in the ground and excited states in a tokamak plasma

X-ray spectra of He-like argon (${\mathrm{Ar}}^{+16}$) have been obtained for the transitions 1snp\ensuremath{\rightarrow}1${s}^{2}$, with 3\ensuremath{\le}n&lt;\ensuremath{\infty}, from Alcator-C tokamak plasmas. In the periphery of the plasma, the n=9 and 10 and 15&lt;n\ensuremath{\le}40 levels are observed to be predominantly populated by charge transfer between ${\mathrm{Ar}}^{+17}$ and intrinsic neutral hydrogen in the ground and first few excited states. Neutral hydrogen density pro- files are deduced from these measurements. The first experimental observations of the reactions ${\mathrm{Ar}}^{+17}$(1s ${\mathrm{}}^{2}$S)+${\mathrm{H}}_{0}^{\mathrm{*}}$(n=2,3) \ensuremath{\rightarrow}${\mathrm{Ar}}^{+16\mathrm{*}}$(1snp ${\mathrm{}}^{1}$P)+${\mathrm{H}}^{+}$ are presented and their cross sections are estimated.