Dissociation of water molecules upon keV H⁺- and He^q+-induced ionization

Abstract

The interaction of keV H+, He+ and He2+ ions with gas-phase H2O molecules leads to formation of H2Oq+ ions which subsequently can undergo dissociation into various fragment species. From coincident determination of the fragment-ion kinetic energies, kinetic energy releases (KER) for the different dissociation channels are obtained. We present the KER values for the various dissociation channels at different projectile kinetic energies. For He+, extraordinarily large relative dissociation yields are observed as compared to H+ and He2+. For both singly charged projectiles we observe 14.5 eV H+ fragments, most probably due to the two-step H2O2+→ HO2+ + H → H+ + O+ + H process predicted 5 years ago (Nobusada K and Tanaka K 2000 J. Chem. Phys. 112 7437).

Ionization of small molecules induced byH+, He+, andKovács1, Herczku2, Juhász3 et al. 2016Phys. Rev. A

“…Molecular ionization is often followed by the dissociation of the molecule. The connection between ionization and fragmentation is a subject of numerous studies and has been intensively investigated [17][18][19].…”

Dissociative ionization of the H2O molecule induced by medium-energy singly charged projectiles

“…The dissociation of small few-atom molecules has been extensively studied by the impact of various types of projectiles, such as photons [1][2][3], electrons [4,5], protons [6][7][8], and multiply charged ions [9][10][11][12][13]. Molecular fragmentation by ion impact is a rather complex process, which is highly interesting in different areas from astrophysics to cancer therapy.…”

“…The fragmentation pattern of a target molecule is determined by the velocity, charge state, and structure of the projectile [10] and the open fragmentation channels taking place in the reaction [9]. By the collision, the target molecule may fall to several possible excited and ionized states.…”

“…The emitted fragments * kovacs.sandor@atomki.mta.hu can be neutral or charged particles in excited or ground states [7]. There are also two-or three-step fragmentation processes [7,10,19] Note that a fragmentation channel is usually characterized by the charge states of the precursor ion and the fragments, without specifying their electronic, vibrational, or rotational states. Accordingly, the same channel notation may be used for a set of subchannels with different kinetic energy release (KER) values.…”

“…In most of the experiments, the dissociation pattern of water was studied thoroughly only for the low-charge-state transient molecular ion (H 2 O q+ , where q 3) [4,5,9,10,14,15,22,23]. In a recent work Pedersen et al [2] studied the dissociation of the H 2 O 2+ molecular ion in detail, induced by XUV photons from H 2 O + ions.…”