Populations of np terms in deuterium atoms emergent from carbon foils bombarded with D +, D 2+ and D 3+ ions

Abstract

We have measured relative beam-foil populations of 2p, 3p, and 4p terms in D 0 as a function of the projectile energy (20 ≲ E M ≲ 500 keV amu ) for D +, D 2 +, and D 3 + ions impinging on carbon foils of various thicknesses (≅ 2–20 μg cm 2 ). With D + projectiles, the np populations reach their equilibrium values even in the thinnest foils used. We compare the dependence on energy of these populations to the equilibrium neutral fraction variation for hydrogen (deuterium) beams emerging from a carbon foil and deduce some information concerning beam-foil populations. When molecular projectiles pass through very thin foils, well known molecular effects appear which depend on the dwell time, t, i.e., the time spent by the projectile in the foil. In this work we consider only the long-dwell-time region t > 2 × 10 −15 s. We study the variation of R α = I molec / I atom ( I molec and I atom are the Ly-α intensities per incident deuteron (proton) observed with molecular and atomic projectiles of the same velocity, respectively) with the projectile energy per nucleon ( E M ) and the thickness ( T) of the foil. For a foil of given thickness, R α increases with E M> and reaches a saturation value R ∞ which decreases when T increases. These results, in agreement with our previous measurements using hydrogen projectiles, indicate that t is not the only parameter relevant to molecular effects. Comparisons are reported between R> α(E M> ) values obtained (a) with H 2 + and D 2 + projectiles and (b) with D 2 + and D 3 + projectiles, using foils of various given thicknesses. Ratios R β(E M ) and R γ(E M ) are also measured using Ly-β and Ly-γ radiations and compared to R α(E M ) values. An interpretation for some of our results is proposed.