Ionization and solvation of HCl adsorbed on the D2O-ice surface

Abstract

The interaction of HCl with the D(2)O-ice surface has been investigated in the temperature range 15-200 K by utilizing time-of-flight secondary ion mass spectroscopy, temperature-programmed desorption, and x-ray photoelectron spectroscopy. The intensities of sputtered H(+)(D(2)O) and Cl(-) ions (the H(+) ions) are increased (decreased) markedly above 40 K due to the hydrogen bond formation between the HCl and D(2)O molecules. The HCl molecules which form ionic hydrates undergo H/D exchange at 110-140 K and a considerable fraction of them dissolves into the bulk above 140 K. The neutral hydrates of HCl should coexist as evidenced by the desorption of HCl above 170 K. They are incorporated completely in the D(2)O layer up to 140 K. The HCl molecules embedded in the thick D(2)O layer dissolve into the bulk, and the ionic hydrate tends to segregate to the surface above 150 K.

Hydration of ammonia and hydrogen chloride at cryogenic temperature studied by TP-TOF-SIMS

“…To date, TP-TOF-SIMS has revealed that both HCl and NH 3 molecules adsorbed on pure ASW films are hydrated considerably up to 140 K [22][23][24], which is consistent with the conclusions drawn using different approaches [3][4][5][6]8,9,13,14]. However, very little is known about intermolecular interactions at the surface of acidic and basic water-ice films including hydrated HCl or NH 3 molecules, respectively.…”

“…NH þ 4 þCl À ðH 2 OÞ n ). The latter is more likely, as inferred from our results [23] showing that neutral HCl molecules are incorporated into the bulk while ionic hydrates [i.e., (H 3 O) + Cl À (H 2 O) nÀ1 ] stay at the surface or in subsurface sites. In any case, the direct contact between NH 3 and HCl or Cl À is prerequisite for the increase in NH þ 4 intensity.…”

“…Fig. 1(a) shows temperature evolutions of the intensities of typical secondary ions sputtered from the D 2 O-ice film (50 ML) on which 1 ML of the HCl molecule was adsorbed at 15 K. Details of this system were described previously [23]. H + and D + ions are emitted basically from dangling Cl-H and O-D bonds.…”

“…Likewise, it is recognized that NH 3 molecules transport into the water-ice bulk [8,[19][20][21]. Previously, we revealed that NH 3 and HCl molecules adsorbed on amorphous solid water (ASW) dissolve in the bulk up to 140 K [22][23][24]. This phenomenon has been ascribed to the emergence of a liquid-like phase.…”

Photodissociation of Molecules in Pure and Doped Water and in Nitrogen Heterocyclic Clusters in the Excited State

“…In matrix isolation spectroscopy such a transition was claimed, although the assignment of the bands to the correct size is difficult [53]. The HX dissociation has been theoretically studied on model ice surfaces [57][58][59][60][61][62], and it has also been the subject of extensive experimental investigations using temperature controlled desorption, X-ray absorption spectroscopy, reactive Cs þ ion scattering, low energy sputtering and Fouriertransform infrared spectroscopy [63][64][65][66][67][68][69][70][71]. On the other hand, vibrational spectroscopy of free HCl(H 2 O) n clusters could only unambiguously identify covalently bound species up to n ¼ 2 [55,56].…”