NMR in a Diamond Anvil Cell, Ruby Fluorescence, and the Ultra-high Pressure Scale

9971326 silvera该项目在高压金刚石砧细胞（DAC）物理方面有三个重点：核磁共振；红宝石压力标度的扩展与红宝石的物理性质。在DAC中，一种很有前途的核磁共振新几何结构已经将该技术的压力范围扩大了2倍以上，达到几百千巴。该技术将扩展到兆巴压力。对了解高压氢的性质很重要的正对位转化将通过核磁共振直接研究这些高压。高压相涉及定向排序。在从有序相到无序相的过程中，氢中的Pake重态坍缩为单重态，可以观察到相线。氢金属化的理论计算预测，分子键会随着压力的增加而收缩，然后增大。键长可以通过Pake双重态的分裂来研究。在DAC中，红宝石荧光光谱是测定压力的最重要手段。目前，准流体静力刻度只能校准到80 GPa；我们将在同步加速器上将其扩展到数兆巴范围，在相同压力下同时测量红宝石光谱和已知压力标记的状态方程。我们还将研究红宝石的固相，因为预测相的变化在该地区很少受到关注，也会影响红宝石的压力范围。扩展到兆巴压力范围的高压研究是物理学中一个迅速发展的领域。在这个项目中，研究生和本科生都接受了在桌面上的金刚石砧细胞（dac）中产生高压的方法的培训。核磁共振的方法将扩展到兆巴压力，研究氢及其同位素的样本。红宝石将在同步辐射源的兆巴压力范围内进行研究，以了解其结构，同时也产生了兆巴范围内压力的重要新校准。***

9971326SilveraThis project has three thrusts in high pressure diamond anvil cell (DAC) physics: NMR; extension of the ruby pressure scale and the physics of ruby. A promising new geometry for NMR in a DAC has already extended the pressure range for this technique by more than a factor of 2 to a few hundred kilobars. The technique will be developed to extend to megabar pressures. Ortho-para conversion, important for the understanding of the properties of high pressure hydrogen will be studied directly by NMR to these high pressures. High pressure phases involve orientational ordering. Phase lines can be observed by the collapse of the Pake doublet in hydrogen to a singlet in going from the ordered to disordered phase. Theoretical calculations of metallization of hydrogen predict that the molecular bond shrinks then grows with increasing pressure. The bond length can be studied from the splitting of the Pake doublet. In a DAC the ruby fluorescence spectrum is the most important means of determining pressure. Currently, the quasi-hydrostatic scale is only calibrated to 80 GPa; we shall extend this to the multi-megabar range at a synchrotron, doing simultaneous measurements of the ruby spectrum and the equation of state of known pressure markers under the same pressure. We shall also study the solid phases of ruby as predicted phase changes have received little attention in this region and can also impact on the ruby pressure scale.%%%High pressure research extending into the megabar pressure range is a rapidly growing field of physics. In this program both graduate and undergraduate students are trained in methods of generating high pressure in Diamond Anvil Cells (DACs) on a table-top. Methods of nuclear magnetic resonance will be extended to megabar pressures, studying samples of hydrogen and its isotopes. Ruby will be studied in the megabar pressure range at a synchrotron radiation source to understand its structure, also producing an important new calibration of pressure in the megabar range.***