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

Abstract

We investigated the dipolar reorientation of acetone molecules in amorphous solids under the influence of externally applied electric fields in the range of (0−4.3) × 10 8 V· m −1 . The electric field was applied using an ice film capacitor method, and the field strength was estimated from measurements of the film voltage and thickness using a Kelvin probe and the temperature-programed desorption method, respectively. Reorientation of the acetone molecules was monitored with reflection−absorption infrared spectroscopy (RAIRS), which measured the absorbance change of the acetone vibrational bands induced by the applied electric field. The electric field caused a substantial degree of dipolar polarization of the sample. Acetone molecules were reoriented toward the field direction by an average angle of about 31°at an applied field strength of 4.3 × 10 8 V·m −1 , according to analysis of the RAIRS intensity changes using a simple molecular geometry model. While the extent of dipolar polarization of the sample increased with increasing field strength, the sample was not reversibly depolarized with decreasing field strength.Multiple-peak analysis of the ν(CO) spectrum revealed that the molecules in the acetone− water boundary region were more easily rotated compared to those in the bulk.

Entropy-Driven Spontaneous Reaction in Cryogenic Ice: Dissociation of Fluoroacetic Acids

“…In one chamber (A), the sample temperature was variable in the range of 70−1200 K using a closed-cycle helium cryostat and resistive heating. 4 In the other chamber (B), the temperature was varied between 8 and 1200 K using a closed-cycle helium cryostat with better cooling efficiency and electron bombardment (2 keV) heating. 27 Frozen molecular films of interest were grown on Pt(111) substrate surfaces cooled at a desired temperature.…”

“…The experiments were conducted in two ultrahigh vacuum chambers, both equipped with instrumentation for RAIRS and temperature-programmed desorption (TPD) mass spectrometry. In one chamber (A), the sample temperature was variable in the range of 70–1200 K using a closed-cycle helium cryostat and resistive heating . In the other chamber (B), the temperature was varied between 8 and 1200 K using a closed-cycle helium cryostat with better cooling efficiency and electron bombardment (2 keV) heating .…”

“…We prepared a mixture of acid and D 2 O in solid form by condensing their vapors onto a Pt(111) substrate at low temperature inside an ultrahigh vacuum chamber. 4 The acid− D 2 O mixture in the form of a thin film (thickness 40−80 monolayers; MLs) was sandwiched between two D 2 O spacer layers (thickness 20−30 MLs) to protect the acid molecules from being exposed at the sample surfaces. Reflection absorption infrared spectroscopy (RAIRS) was used to detect molecular and dissociated forms of the acids.…”

Brute Force Orientation of Matrix‐Isolated Molecules: Reversible Reorientation of Formaldehyde in an Argon Matrix toward Perfect Alignment

“…A static DC electric field was applied across the film by using the ice film nanocapacitor method, which was described in detail previously . The field strength was increased by the deposition of Cs + ions on the D 2 O film surface, whereas the field strength was decreased by exposing the Cs + ‐deposited film to low energy (roughly 5 eV) electrons . The external field strength applied to the Ar matrix region was estimated from the film voltage by considering the division of the voltage between the Ar and D 2 O layers [Eq.…”

Solid Ammonia Charging by Low-Energy Electrons

“…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 …”