Charge exchange and dissociative processes in collisions of slow He{sup 2+} ions with H{sub 2}O molecules

Journal Article · Tue Feb 01 00:00:00 EST 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.71.022705· OSTI ID:20650085

Seredyuk, B; McCullough, R W; Tawara, H; Gilbody, H B; Bodewits, D; Hoekstra, R; Tielens, A G.G.M.; Sobocinski, P; Pesic, D; Hellhammer, R; Sulik, B; Stolterfoht, N; Abu-Haija, O; Kamber, E Y ^[1]

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1. Queen's University Belfast, Belfast BT7 1NN (United Kingdom)

Experimental and theoretical studies of one-electron capture in collisions of He{sup 2+} ions with H{sub 2}O molecules have been carried out in the range 0.025-12 keV amu{sup -1} corresponding to typical solar wind velocities of 70-1523 km s{sup -1}. Translational energy spectroscopy (TES), photon emission spectroscopy (PES), and fragment ion spectroscopy were employed to identify and quantify the collision mechanisms involved. Cross sections for selective single electron capture into n=1, 2, and 3 states of the He{sup +} ion were obtained using TES while PES provided cross sections for capture into the He{sup +}(2p) and He{sup +}(3p) states. Our model calculations show that He{sup +}(n=2) and He{sup +}(n=3) formation proceeds via a single-electron process governed by the nucleus-electron interaction. In contrast, the He{sup +}(1s) formation mechanism involves an exothermic two-electron process driven by the electron-electron interaction, where the potential energy released by the electron capture is used to remove a second electron thereby resulting in fragmentation of the H{sub 2}O molecule. This process is found to become increasingly important as the collision energy decreases. The experimental cross sections are found to be in reasonable agreement with cross sections calculated using the Demkov and Landau-Zener models.

• OSTI ID: 20650085
• Journal Information: Physical Review. A, Vol. 71, Issue 2; Other Information: DOI: 10.1103/PhysRevA.71.022705; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
CATIONS
CHARGE EXCHANGE
CROSS SECTIONS
DISSOCIATION
ELECTRON CAPTURE
ELECTRON-ELECTRON COLLISIONS
ELECTRON-ELECTRON COUPLING
ELECTRONS
HELIUM IONS
ION SPECTROSCOPY
ION-MOLECULE COLLISIONS
KEV RANGE
MOLECULES
P STATES
PHOTON EMISSION
POTENTIAL ENERGY
S STATES
SOLAR WIND
WATER