Magnetically Manipulated Molecular Beams: Studying the Structure of Water Surfaces

Physical and Analytical Chemistry Seminar

Lecturer: Elina Lisitsin

29 May 2016 @ 12:30

Location: Faculty Seminar Room

Amorphous-Solid-Water (ASW) is the most abundant form of ice in the universe and extensive efforts are being invested in characterizing its properties, even so there is a great deal of uncertainty and controversy regarding its properties and the various phase transitions it undergoes [1]. The NMR technique is a sensitive tool for studying structure and dynamics of solid state matter. Nevertheless, due to technical difficulties very few NMR studies of water ice have been performed, focusing on crystalline phase (CI) and low and high density amorphous phases obtained by pressurizing CI. To the best of our knowledge NMR experiments have never been performed on vapor deposited ice, i.e ASW.
In this talk I will present development of the first “Magnetic beam surface NMR (MBSN) spectrometer”, an instrument which aims to measure proton NMR signals from deposited mono-layers and even sub-mono-layers of adsorbed water molecules, which could be possible using our magnetically focused ortho-H2O source [2]. I will briefly describe the principle of magnetic focusing, and then I’ll show FTIR measurements to find the purity of the ortho-water beam reaching the sample [3]. At the second part of my talk I will introduce the construction steps of the new MBSN spectrometer and finally show recent NMR measurements which demonstrate that vapor deposited ice exhibits a unique spin-lattice relaxation behavior which is strikingly different from that seen for other forms of ice.
[1] C. A. Angell, Annu.Rev.Phys.Chem.55,559 (2004).
[2] T. Kravchuk et al. Science,331,319 (2011).
[3] E. Lisitsin et al. Physical Review A 86, 062710 (2012)