Phase Transitions in Vapor Deposited Water Under the Influence of High Surface ELectric Fields
Abstract
Field ionization of vapor deposited water on a platinum field emitter was studied over a temperature range of 103-150 K. Water adlayers that were 50 - 3600 A thick were grown under field-free conditions by exposure of a cryogenically cooled emitter tip to water vapor in ultrahigh vacuum. Field ionization was probed by ramped field desorption (RFD) in which desorption of ionic species (hydrated protons) is measured while increasing the applied electric field linearly in time. The dependence of the field required for ionization onset as a function of temperature and water thickness is presented and discussed. In the limit of thin layers the onset field decreased from 0.5 to 0.2 V/A as temperature increased from 105 to 150K. An activation barrier of 0.7 eV (16 kcal/mol) for ionization of amorphous and crystalline water was estimated from the temperature dependence of the onset field. This is in excellent agreement with the 0.74 eV (17 kcal/mol) required to produce a pair of ions from a pair of solvated water molecules.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 24, 1999
- Accession Number
- ADA365073
Entities
People
- Dawn L. Scovell
- Eric M. Stuve
- Tim D. Pinkerton
- Valentin K. Medvedev
Organizations
- University of Washington