Effect of Electric Field on Condensed-Phase Molecular Systems. II. Stark Effect on the Hydroxyl Stretch Vibration of Ice

Abstract

We studied the Stark effect on the hydroxyl stretching vibration of water molecules in ice under the influence of an external electric field. Electric fields with strengths in the range from 6.4 × 10 7 to 2.3 × 10 8 V·m −1 were applied to an ice sample using the ice film capacitor method. Reflection absorption infrared spectroscopy was used to monitor the field-induced spectral changes of vibrationally decoupled O−H and O−D bands of dilute HOD in D 2 O and H 2 O− ice, respectively. The spectral changes of the hydroxyl bands under applied field were analyzed using a model that simulates the absorption of a collection of Starkshifted oscillators. The analysis shows that the Stark tuning rate of ν(O−D) is 6.4−12 cm −1 /(MV·cm −1 ) at a field strength from 1.8 × 10 8 to 6.4 × 10 7 V·m −1 , and the Stark tuning rate of ν(O−H) is 10−16 cm −1 /(MV·cm −1 ) at a field strength from 2.3 × 10 8 to 9.2 × 10 7 V·m −1 . These values are uniquely large compared to the Stark tuning rates of carbonyl or nitrile vibrations in other frozen molecular solids. Quantum mechanical calculations for the vibrations of isolated water and water clusters show that the vibrational Stark effect increases with the formation of intermolecular hydrogen bonds. This suggests that that the large Stark tuning rate of ice is due to its hydrogen-bonding network, which increases anharmonicity of the potential curve along the O−H bond and the ability to shift the electron density under applied electric field.

Electric Field Effect on Condensed-Phase Molecular Systems. IX. Control of Proton Displacement in Matrix-Isolated Hydrogen Chloride–Water Complexes

“…Note that a band splits, rather than broadens, when the frequency shift is large at a strong field and the spectrum is acquired with p-polarized light parallel to the applied electric field direction. 24 External fields applied in this work neither break the complex nor induce reorientation of individual molecules (HCl and H 2 O) constituting the complex because the applied field strength (∼10 8 V/m) is much weaker than the electric field strength of the internal hydrogen bond of the complex (10 9 to 10 10 V/m). 15 The rigidity of the structure and orientation of the complex is supported by the unchanging intensity of the ν stretch (H−Cl) band under electric fields (Figure S2), even when the band undergoes Stark broadening and splitting.…”

“…The splitting of the ν stretch (H–Cl) band into two separate peaks at a stronger field (≥3.2 × 10 7 V/m) manifested a larger Stark shift of ν stretch (H–Cl). Note that a band splits, rather than broadens, when the frequency shift is large at a strong field and the spectrum is acquired with p-polarized light parallel to the applied electric field direction . External fields applied in this work neither break the complex nor induce reorientation of individual molecules (HCl and H 2 O) constituting the complex because the applied field strength (∼10 8 V/m) is much weaker than the electric field strength of the internal hydrogen bond of the complex (10 9 to 10 10 V/m) .…”

Effect of Electric Field on Condensed-Phase Molecular Systems. I. Dipolar Polarization of Amorphous Solid Acetone

“…This paper is the first in a series of two papers investigating the effects of applied electric field on frozen molecular films. The other paper (referred to as Paper II 19 ) immediately follows this one and examines the vibrational Stark effect of water molecules in ice crystals.…”

Solid Ammonia Charging by Low-Energy Electrons

“…The gradual charging of these layers eventually forms strong electric fields, up to 10 9 V/m inside the host matrix. , The locally oriented electric field may serve as a catalyst and as a regulator for reaction mechanisms. , The electric field effect is not limited just to ground-state chemical reactivity but also to excited states and radicals, , thus being relevant to the processing of molecules via photochemistry and mechanisms like DEA. Examples for the effect of strong oriented electric fields on molecules embedded inside ices can be found in the works of Kang and co-workers. ,− …”

“…This was demonstrated mostly by the direct bombardment of amorphous solid water (ASW) films by cations under ultrahigh vacuum (UHV) conditions. ,− The formation of strong internal electric fields can further lead to the preferred alignment of the polarization vector of coadsorbates, frozen molecules within the host molecular ice. By following the development of vibrational Stark effect (VSE), Kang and co-workers demonstrated how such strong fields affect various molecules trapped inside molecular ices. ,− Moreover, chemical reactions were theoretically predicted to be selectively catalyzed and accelerated by orders of magnitude when strong electric fields are oriented along the reaction coordinate …”