Construction and Calibration of a Streaked Optical Spectrometer for Shock Temperature

Here we describe the implementation and calibration of a streaked visible spectrometer (SVS) for optical pyrometry and emission/absorption spectroscopy on light gas gun platforms in the UC Davis Shock Compression Laboratory. The diagnostic consists of an optical streak camera coupled to a spectrometer to provide temporally and spectrally-resolved records of visible emission from dynamically-compressed materials. Fiber optic coupling to the sample enables a small diagnostic footprint on the target face and flexibility of operation on multiple launch systems without the need for open optics. We present the details of calibration (time, wavelength and spectral radiance) for absolute temperature determination and present benchmark measurements of system performance.Comment: 6 pages, 3 figures Davies, E., et al. (accepted). In J. Lane, T. Germann, and M. Armstrong (Eds.), 21st Biennial APS Conference on Shock Compression of Condensed Matter (SCCM19). AIP Publishin

Pressure-induced chemistry in a nitrogen-hydrogen host–guest structure

International audienceNew topochemistry in simple molecular systems can be explored at high pressure. Here weexamine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-raydiffraction, synchrotron infrared microspectroscopy and visual observation. We find aeutectic-type binary phase diagram with two stable high-pressure van derWaals compounds,which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van derWaals host–guest compound in which hydrogen molecules are contained within channels in anitrogen lattice. This compound shows evidence for a gradual, pressure-induced change inbonding from van der Waals to ionic interactions near 50 GPa, forming an amorphousdinitrogen network containing ionized ammonia in a room-temperature analogue of theHaber–Bosch process. Hydrazine is recovered on decompression. The nitrogen–hydrogensystem demonstrates the potential for new pressure-driven chemistry in high-pressurestructures and the promise of tailoring molecular interactions for materials synthesi