Investigation of Double Excitation- Ionization Resonance Profiles of Helium Atom at 10o-80o Angular Range

Abstract

In this work, the angular variations of the He atom for the resonance levels were experimentally measured by electron spectrometer. 200 eV energetic electron beam collided with Helium (He) gas in high vacuum and scattered electrons were detected. Measurements were taken for angular variation for fixed incident electron energy. The experimental setup in the electron collision laboratory consists of an electron gun, as target He atom, two electron energy analyzers, electron detectors, signal processing units and Faraday Electron Cup (FEC). Here, the auto ionization energy levels of the He atom (in the rare gas element series) for 10o-800 angular range were examined. Differential cross section measurements (DCS) of resonance energy levels were inspected for 32,5-35 eV. Although the symmetry states of resonance profiles are more dominant in the small angle range, both symmetrical and asymmetrical structures are observed for larger angles.

Keywords

• Electron spectrometer
• Double excitation
• Autoionization
• Resonance profiles
• Helium atom

Helyum Atomunun İkili Uyarılma-İyonlaşma Rezonans Profillerinin 10o-80o Açı Aralığındaki Değişimlerinin İncelenmesi

Abstract

Bu çalışmada, elektron spektrometresi kullanılarak, Helyum (He) atomunun rezonans düzeylerinin açısal değişimleri ölçülmüştür. 200 eV enerjili elektron demeti, yüksek vakum ortamında He atomları ile çarpıştırılarak koparılan ve saçılan elektronlar dedekte edilmiştir. Elektron spektrometresi deney düzeneği; vakum sistemi, elektron tabancası, hedef gaz He, saçılan ve koparılan elektronları dedekte eden iki elektron enerji analizörü, elektron dedektörleri, sinyal işleme ünitesi ve Faraday Elektron Toplayıcıdan (FET) oluşmaktadır. Bu çalışmada, soygaz element serisinde olan Helyum atomunun kendiliğinden iyonlaşma enerji seviyeleri 10o-80o açı aralığında incelenmiştir. Enerji değerleri 32,5-35 eV olarak alınmıştır. Küçük açılarda rezonans profillerinin simetri durumlarının daha baskın olduğu görülürken, büyük açılara doğru kayıldıkça hem simetrik hem asimetrik yapıda oldukları görülmüştür.

Keywords

• Elektron spektrometresi
• İkili uyarılma
• Kendiliğinden iyonlaşma
• Rezonans düzeyleri
• Helyum atomu

References

1. K. Bartschat and M. J. Kushner, “Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology,”Proc. of the Nat. Ac. of Sciences, 113 (26), 7026-7034, 2016.
2. X. Ren, T. Pflüger, J. Ullrich, O. Zatsarinny, K. Bartschat, D.H. Madison, A. Dorn, “Low-energy electron-impact ionization of argon: Three-dimensional cross section,” Phys. Rev. A, 85, 032702, 2012.
3. N. Oda, F. Nishimura, and S. Tahira,“Energy spectra of electrons from autoionization states in helium by electron impact,” Pyhs. Rev. Letts., 24, 42-45, 1970.
4. R.P. Madden, and K. Codling, “Two-electron excitation states in helium,” Astrophys. Jour.141, 364-375, 1965.
5. J.W. Cooper, U. Fano, and F. Prats,“Classification of two-electron excitation levels of helium,” Phys. Rev. Letts., 10, 518-521, 1963.
6. Z. Zhang, X. Shan, E. Wang, and X. Chen, “Ejected - electron spectroscopy of autoionizing resonances of helium excited by fast-electron impact,” Phys. Rev.A, 85, 062702, 2012.
7. M.E Rudd, “Observation of autoionization levels in He by positive ion bombardment,” Phys. Rev. Letts., 13, 503-505, 1964.
8. S.M. Silverman and E.N Lassettre, “Additional collision cross sections for Helium especially in the ionized continuum,” The J. of Chem.Phys., 40, 1265, 1964.

9. F.G. Fender, and J.P. Vinti, “Doubly-excited states in Helium,” Pyhs. Rev. Letts., 46(1), 77-78, 1934.
10. T. Y. Wu, “Energy states of doubly excited Helium,” Phys. Rev. Letts., 46, 239-239, 1934.
11. T.Y. Wu, “Auto-ionization in doubly excited Helium and the λ320,4 and λ357,7 lines,” American Phys.Soc. Jour. Archi.66, 291-294, 1944.
12. Wm.S Wilson, “Atomic energy states for excited Helium,” Phys.Rev. Letts., 48, 536-537, 1935.
13. A.T. Kiang, S.T. Ma, and T.Y. Wu, , “Attempt to observe the spectrum of doubly excited Helium,” Pys. Rev. Letts., 50, 673-673, 1936.
14. B.H. Bransden, and A. Dalgarno, “The calculation of auto-ionization probabilities-I: Perturbation methods with application to auto-ionization in Helium,” Pro.of the Phys. Soc., Sec. A, 66, 904, 1953.
15. R.K. Propin,“Calculation of the probability of autoionization in Helium and Lithium atoms,” Opt. and Spec., 8, 158-162, 1960.
16. J.W. Cooper, U. Fano, and F. Prats, “Classification of two-electron excitation levels of helium,” Phys. Rev. Letts., 10, 518-521, 1963.
17. P.G. Burke, D.D. McVicar, and K. Smith, “Calculation of autoionization levels in He,” Phys.Rev. Letts., 11, 559-561, 1963.
18. T.F. O'Malley, and S. Geltman, “Compound-atom states for two-electron systems,” Phys.Rev. Letts, 137, 1344-1352, 1965.
19. U. Fano, “Effects of configuration interaction on intensities and phase shifts,” Phys. Rev., 124, 1866-1878, 1961. M. Domke, C. Xue, A. Puschmann, T. Mandel, E. Hudson, D.A. Shirley, G. Kaindl, C.H. Greene, H.R. Sadeghpour, and H. Petersen, “Extensive double-excitation states in atomic helium,” Phys.Rev. Letts., 66, 1306-1309, 1991.
20. D.G. McDonald, and A. Crowe, “Electron impact excitation-autoionization of the (2s2)1S and (2s2p)3P states of Helium,” J. of Phys. B: At.c, Mol. and Opt. Phys., 25, 4313-4324, 1992.
21. F. Gelebart, R.J. Tweed, and J. Peresse, “Measurements of the absolute differential cross section for autoionization from the levels (2s2p)3P and (2s2)1S of Helium,” J. of Phys. B: At. and Mol. Phys., 7, 174-178, 1974.
22. Ö. Şişe, D. J. Manura, and M. Doğan, “Exploring focal and aberration properties of electrostatic lenses through computer simulation,” Eur. J. of Phys., 29, 1165-1176, 2008.
23. J. Jureta, A.R. Milosavljevic, and B.P. Marinkovic, “High-energy electron impact study on autoionizing region in helium by detection of ejected electrons,” Int. Jour. of Mass Spec., 365, 114-120, 2014.
24. A. Pochat, R.J. Tweed, M. Doritch, and J. Peresse, “Double and triple differential cross sections for autoionisation of helium by electron impact,” J. of Phy. B: At. and Mol. Phys., 15, 2269-2283, 1982.
25. J. Lower, and E. Weigold, “Correlations in the autoionising region of He measured by the (e,2e) technique,” J. of Phys. B: At., Mol. and Opt. Phys., 23, 2819-2845, 1990.
26. A Crowe, D.G. Mcdonald, S.E. Martın, and V.V. Balashov, “Studies of autoionization with (e,2e) spectroscopy,” Can. Jour. Phys., 74, 736-742, 1996.
27. M.J. Brunger, O. Samardzic, A.S. Kheifets, and E. Weigold, “A study of autoionization phenomena in helium using (e, 2e) spectroscopy,” J. of Phys. B: At., Mol. and Opt. Phys., 30, 3267-3285, 1997.
28. O. Samardzic, L. Campbell, M.J. Brunger, A.S. Kheifets, E. Weigold, “Autoionization in electron-helium collisions: an (e,2e) investigation,” J. of Phys. B: At., Mol. and Opt. Phys., 30, 4383-4394, 1997.
29. M. Doğan, B. Lohmann, D. Cvejanovic, and A. Crowe, “A complete experimental study of electron impact ionization, abstracts of contributed papers,” XXII ICPEAC (Int. Conf. on Ph., Elect. and At. Col.), Santa Fe, 18-24 Temmuz, 181-187, 2001.
30. M. Doğan, and A. Crowe, “Coincidence studies of the influence of resonances on simultaneous ionization-excitation of helium by electron impact,” J. of Phys. B: At., Mol. and Opt. Phys., 35, 2773-2781, 2002.
31. M. Doğan, “Correlation studies of simultaneous excitation-ionization in helium,” Doktora Tezi, Univ. of Newcastle upon Tyne, Newcastle, 1999.
32. M. Ulu, “Elektron-Elektron Çakışma Deney Düzeneğinin Durulması ve Düzeneğin Simülasyonu,” Doktora Tezi, Selçuk Üniv., Fen Bil. Enst., Konya, 2007.
33. M. Ulu, Ö. Sişe, and M. Doğan, “Optimizing the performance of an electron gun design followed by lenses and apertures,” Rad. Phys. and Chem., 76, 636-641, 2007.
34. Ö. Şişe, “Helyum Atomunun Kendiliğinden İyonlaşma Tesir Kesitlerinin (e,2e) Çakışma Tekniği ile Ölçülmesi,” Doktora Tezi, Sakarya Üniv., Fen Bil. Enst., Sakarya, 2011.
35. Z.N. Özer, “Elektron-Elektron Çakışma Tekniği (e,2e) ile H2 Molekülünde Young Tipi Girişim Etkilerinin İncelenmesi,” Doktora Tezi, Gebze Yüksek Tek. Enst., Gebze, 2013.
36. I. Bray, D. Fursa, “Electrons and photons colliding with atoms: development and application of the convergent close-coupling method,” J. of Phys. B: At., Mol. and Opt. Phys., 35, 117-146, 2002. J. Frank, and G. Hertz, “Über zusammenstösse zwischen electronen und den molekülen des quecksilberdampfes und die ionisierungsspannung desselben,” Ver. der Deutsc. Physikalisch. Ges., 16, 457-467, 1914.
37. N. Kayar, “Helyum atomunun ikili uyarılma-iyonlaşma rezonans profillerinin açısal değişimlerinin incelenmesi,” Yüksek Lisans Tezi, Afyon Kocatepe Üniv., Fen Bil. Enst., Afyonkarahisar, 2017.
38. A. Lahmam-Bennani, “Thirty years of experimental electron-electron (e,2e) coincidence studies: achievements and perspectives,” J. of Elec. Spec. and Rel. Phen., 23 (2-3), 365-376, 2002.
39. P. Lenard, “Über die absorption von kathodenstrahlen verschiedener geschwindigkeit,” Ann. der Phys., 317, 714-744, 1903.
40. M. Yavuz, “Elektron Etkisi ile Metan Molekülünün İkili Diferansiyel Tesir Kesitlerinin Ölçülmesi,” Yüksek Lisans Tezi, Afyon Kocatepe Üniv., Fen Bil.Enst., Afyonkarahisar, 2013.
41. Z.N. Ozer, N. Kayar, H.A. Yalım, “Experimental study of double excitation-ionization resonance profiles of helium by electrons”, in 4th Int.Conf. on Theo.l and Exp.Studies in Nuc.App. and Tech., 2018, Antalya, p.95.