Physics Colloquium: Dense solid phases of oxygen: molecular interaction at high pressure using synchrotron x-ray probes

Event Details

  • Speaker(s): Yue Meng
  • Date:
  • Time: 4:00 p.m.
  • Location: SCIE 1511 - Atrium Wing

When compressed at room temperature, molecular oxygen undergoes a series of phase transitions and displays marked changes in color, density, vibrational dynamics, and electronic and magnetic properties including metallization and superconductivity. These remarkable phenomena in condensed phases of oxygen are consequences of pressure-induced changes in electronic structure and bonding, an area of fundamental importance but previously inaccessible by in-situ high-pressure studies. Recent development of high-pressure inelastic synchrotron x-ray scattering experimental technique has made it possible to directly probe the bonding changes in low-Z materials in-situ under high pressure. Using this technique, O K-edge spectroscopy investigation has been conducted in pressure range from 2.3 to 38 GPa, where oxygen exists in the dense fluid and solid ?, δ and ? phases. The study has revealed intriguing changes in intermolecular interaction of oxygen with increasing pressure which leads to molecular clustering in the ? phase. The presentation will also include a study of oxygen-nitrogen system using x-ray diffraction and Raman spectroscopy. Instead of forming the expected molecular phases, adding nitrogen into an oxygen system yields ionic compounds under pressure, an illustration of the diverse behavior of 2nd-row molecules under high-pressure conditions