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Interference effect in heavy ion collisions with H 2 :

Interference effect in heavy ion collisions with H 2 : By comparing the experimental electron spectrum from atomic H. L. C. Tribedi. Deepankar Misra , U. Kadhane, Y.P. Singh Tata Institute of Fundamental Research, Colaba, Mumbai-400 005, India . Pat Richard, JRM, KSU P. Fainstein.

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Interference effect in heavy ion collisions with H 2 :

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  1. Interference effect in heavy ion collisions with H2: By comparing the experimental electron spectrum from atomic H. L. C. Tribedi. Deepankar Misra , U. Kadhane, Y.P. Singh Tata Institute of Fundamental Research, Colaba, Mumbai-400 005, India. Pat Richard, JRM, KSU P. Fainstein

  2. Another view

  3. Tata Institute, Mumbai (Bombay) TIFR On Arabian Sea

  4. Detection of low energy electrons emitted in atomic collisions provide crucial information on the various ionization-mechanisms. The e-DDCS spectrum identifies different processes such as soft electrons (SE), electron capture in continuum (ECC) cusp and the binary encounter (BE). In addition, the e-spectra from H2, is very rich since it can provide the evidence of theinterference effect. Since the two H-atoms in molecular hydrogen are indistinguishable, their contributions to the ionization add coherently and an interference effect might be expected. Introduction

  5. VOLUME 87, NUMBER 2 PHYS ICAL RE V IEW LETTERS 9 JULY 2001Evidence for Interference Effects in Electron Emission from H2Colliding with 60 MeVu Kr34+IonsN. Stolterfoht et al.

  6. RAPID COMMUNICATIONSPHYSICAL REVIEW A 67, 030702(R) (2003)Interference effects in electron emission from H2 by 68-MeV’uKr33ø impact:Dependence on the emission angleN. Stolterfoht et al. Experimental-to-theoretical ratio Zeff=1.19 for H

  7. The electrons emitted from H2 were detected by an hemispherical electrostatic analyzer between 1 and 1000 eV for 10-12 angles between 150 and 1500. We show “fully measured” (Experiment with atomic Hydrogen ) interference oscillation for relatively lower collision energies: 1-2.5 MeV/u C6+ and F9+ on H2/H. Also derived the oscillations using Calculated DDCS for H : 6 MeV/u C6+ + H2. Experimental Details

  8. HV1 HV2 Vcom Shaft CEM Analyzer Turn Table 700 l/Sec Diff Stack CEM HV & Signal Gas Inlet M.K.S. Turbo 1000 l/Sec Ionization Gauge Experimental Setup Slit System F.C.

  9. Block Diagram TFA BIAS CEM CFD Electrostatic Analyzer F.C. HV1 HV2 C.I. DAC1 DAC2 Computer RS-232 DAC4 DAC3 Scalar Microcontroller

  10. Energy Distribution. Energy Distribution of secondary electrons emitted from H2 by collision with6MeV/u.bare C ions.

  11. Energy Distribution6 MeV/u C6+ + H2

  12. Angular Distribution. Angular Distribution of secondary electrons emitted from H2

  13. Interference at different angles. 6 MeV/u C6+ + H2

  14. 6 MeV/u C6+ + H2.:45o,75o. Dependence of the phase and amplitude of the oscillation on different choices of effective target atomic number (ZT) in the calculation of DDCSfor H.

  15. Interference in backward angles. Frequency of oscillation is higher in backward angles compared to forward angles, as predicted by theoretical model.

  16. Expt at JRML, KSU

  17. “Fully Measured” interference structure. Fully Measured DDCS Ratio for H2 & H. Dependence on projectile atomic number is investigated. Accepted in Phys. Rev. Lett. 2004.

  18. Comparison between different methods. Fully Measured DDCS Ratio for H2 & H. Experimentally measured Cross section for H was used to derive the interference oscillations and a comparison was made. (using theoretical values for atomic H)

  19. Absolute DDCS for H and ratio Tribedi, Richard et al. J.Phys.B (letts.) 31, L3691998 The oscillation in the ratio was observed by us even earlier

  20. Interference effect is not only a phenomena of high energy collisions. It is important at relatively low collision energies also. The dependence of the oscillations on the projectile atomic number is very weak. First study of “fully measured” ratios giving a direct evidence of the interference effect. Present method isfree from: i) the normalization procedure. ii) choice of theoretical parameters like ZT iii) systematic experimental errors. Conclusions [D. Misra, UK, YPS, LCT Richard, PF (PRL 2004, in press)]

  21. [1] N. Stolterfoht et al., Phys. Rev. Lett., 87 023201 (2001). [2] M.E. Gallasi et al., Phys. Rev A 66, 052705 (2002). [3] L. Nagy et al., J. Phys. B 35, L453 (2002). [4] Deepankar Misra et al., ( Accepted in Phys. Rev. Lett.,) References

  22. 6 MeV/u C6+ + H2: 300 Frequency doubling and Double Scattering.

  23. 2 2 2 1 1 1 (T1G0T2) (T1+T2) (T2G0T1) Single Scattering Double Scattering T = (T1+T2) + (T2G0T1 + T1G0T2) + (T2G0T1G0T2 + T1G0T2G0T1) + … T1 = V1 + V1G0V1 +V1G0V1G0V1+… T2 = V2 + V2G0V2 +V2G0V2G0V2+… k k’ k’’ k k0 k0 k k0 k0 = q - k

  24. 6 MeV/u C6+ + H2: 600 A double scattering model is considered. The electrons emitted from one center get scattered by the other center, giving rise to a doubling of the frequency in the interference oscillations.

  25. Experimental Technique Electron spectroscopy: ****C60 vapour source (450-500o C) *** Hemispherical Electron Analyzer. *** Preaccleration voltage = +5V *** m-metal shielding used to reduce mag. Field (below 5 mG) *** Gas pressure kept low : 0.1 mTorr *** electrons between 1 eV to 6 keV ****12 angles between 200 – 1600 degree

  26. X- Ray and electron emission in heavy ion collisions with fullerenes and solids: The collective response Lokesh C Tribedi Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India Students: U.Kadhane D. Misra Y.P.Singh, Aditya Kelkar : Post doc: Ajaykumar Sc. And Tech. Staff : K.V.Thulasiram W. Fernandez And Pelletron Accelerator Staff

  27. X-ray set up with Pelletron 14 MV Pelletron Accelerator And a LINAC booster coming up

  28. n=3 n=2 Target n=1 Projectile

  29. Typical Lyman x-ray spectra

  30. Lyman Ratios for gases and C60

  31. The ratio of Lyb/ Lya for solid and gas GANIL Expt., V=36 a.u. Bare Kr ions on C,Al, Cu and N2 & Ar Rozet et al. The Lyman ratio is 20-25% Lower for solids w.r.t gases

  32. Lyaintensity for solid and gasEffect of wake field and Stark mixing ws= 2so, 2po=3.8 eV for S Stark mixing of 2so & 2po in strong wake field (109 V/cm) in a very small time scale 5.10-17sec. Population changes in 2s and 2p Metastable 2s Small 2s-1s M1 transition (3%) Lya enhancement Parameters: td, wp, ws, f, tp

  33. Wake phenomena and e-density fluctuations: Echenique, Ritchie, Brandt;and Burgdoerfer

  34. Comparison of the ratio i.e. C60 / N2 Difference ~ 15%\i() (for capture) • Model predicts ~ 10% • Other mechanisms: Post collisional effect! • Effect of Giant dipole polarization and Stark mixing! Kadhane et al PRL 90 093401 (2003)

  35. A comparative study ions Z/ V Quantity Solid st. effect td (s) • Kr36+ 1.0 Ly ratio 20-25% ~ 10-15 • S16+ 1.3 Ly-ratio 15% ~5.10-17 • Cl17+ 1.4 Ly ratio 20 % ~5.10-17 • Si/S/Cl 1.1-1.5 REC 40-50% • C/O/F <0.5-1 REC No measurable effect

  36. Ly ratio in collisions with Cl17+ C60

  37. E-DDCS spectrum of C60

  38. Future? • A new ion source, 14.5 GHz ECR source, (obtained from Pantechnik, France) will be installed dedicated mainly for atomic collisions in the low energy region. • It will be coupled with a 300 kV accelerator. • High resolution x-ray, electron spec, ToF • Noble gas cluster/ fullerenes • May be coupled with a laser • ……….. • ………..

  39. The Fragmentation Recoil Ion Spectra of C60 Evaporation

  40. Electron density distribution along trajectory in C60 Hadjar, Hoekstra, Morgenstern, Schlatholter, PRA 63, 033201 (2001)

  41. Total Ly x-ray cross section due to capture *The CDW over estimates the cross sections at v=13 *CDW reproduces the data at v=36 a.u. *Higher order terms play a role giving saturation *The data for C60 falls on “gas-line”

  42. We are at work!!Electron spectroscopy set up

  43. FUTURE PLAN Charge-state analysis X-ray Umesh Yeshpal TOFMS Electron Spec. Umesh Deepankr

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