Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect

MISRA, D.; KELKAR, A.; KADHANE, U.; KUMAR, A.; SINGH, Y. P.; TRIBEDI, L. C.; FAINSTEIN, P. D.

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Año: 2007 vol. 75 p. 5271 - 5271

1050-2947

We report the energy and angular distribution of electron doubledifferential cross sections (DDCS) in collision of 6-MeV/uC6+ions with molecular hydrogen. We explain the observed distributions interms of the two-center effect and the Young-type interference effect.The secondary electrons having energies between 1 and 1000eV aredetected at about 10 different emission angles between 30° and150° . The measured data are compared with the state-of-the-artcontinuum distorted wave-eikonal initial state and the first Born modelcalculations which use molecular wave function. The single differentialcross sections are derived and compared with the theoreticalpredictions. The oscillations due to the interference effect are derivedin the DDCS ratios using theoretical cross sections for the atomic Htarget. The effect of the atomic parameters on the observed oscillationsis discussed. An evidence of interference effect has also been shown inthe single differential cross section. The electron energy dependence ofthe forward-backward asymmetry parameter shows a monotonicallyincreasing behavior for an atomic target, such as He, which could beexplained in terms of the two-center effect only. In contrast, for themolecular H2 the asymmetry parameter reveals an oscillatorybehavior due to the Young-type interference effect superimposed with thetwo-center effect. The asymmetry parameter technique provides aself-normalized method to reveal the interference oscillation which doesnot require either a theoretical model or complementary measurements onthe atomic H target.