Cold Atoms, Cold Molecules, and Spectroscopy

根据这项赠款开展的工作包括两个部分。其中一个组成部分将涉及对玻色-爱因斯坦凝聚体中冷原子系综的理论建模，在这种凝聚体中，所有原子都处于最低量子能级，温度低于绝对值微度。最近的许多实验，包括石溪的一些实验，都是在周期势下对这样的原子系综进行的。这些实验可以以一种可控的方式模拟半导体或超导体等晶体固体中的周期性电势。一个需要解决的问题是，当施加周期势时，原子是否保持在最低量子态，或许是突然施加，还是激发被诱导。理论工作将有助于解释最近关于这一点的实验观察结果。另一个组成部分是在世界各地的几个实验室工作，这些实验室旨在生产也是在纳米开尔文温度下的超低温双原子分子。近年来，我们一直在分析双原子分子的光谱数据，以便能够告诉实验者使用什么激光波长来诱导两个冷原子结合成一个冷分子。下一阶段的工作是分析核自旋结构(类似于核磁共振成像中使用的效应)的影响，这种结构在某些方案中变得占主导地位。考虑到这项工作的更广泛影响，可以说，原子和现在双原子分子的极低温度的达到，使人们能够克服常温下的平均效应，当时大量的量子能级被占据。通过选择处于最低量子态的粒子，就有可能获得关于它们相互作用和行为的更精确的信息。通过改变施加在冷原子上的条件，可以更好地理解复杂的自然发生系统中发生的效应。例如，周期性激光光场可以模拟晶格中的周期性势能，但可以在一定的晶格幅度和波长范围内进行。这已经对高温(50开尔文以上)超导现象以及原子核内复杂的相互作用产生了新的见解。超导体现在被用于许多研究应用。它们在高电流密度地区的电力传输中的使用可以提高美国电网的效率。

The work to be performed under this grant consists of two components. One component will involve theoretical modeling of ensembles of cold atoms in a Bose-Einstein condensate, in which all atoms are in the lowest quantum level, at temperatures less than a microdegree absolute. Many recent experiments, including some at Stony Brook, have been performed on such atomic ensembles when placed in a periodic potential. These experiments can mimic, in a controllable way, the periodic potential in a crystalline solid, such as a semiconductor or superconductor. One question to be addressed is whether the atoms remain in the lowest quantum state when the periodic potential is applied, perhaps suddenly, or whether excitations are induced. The theoretical work will help to interpret recent experimental observations on this point. The other component pertains to work in several laboratories world-wide directed to the production of ultra-cold diatomic molecules, also at nanoKelvin temperatures. In recent years, we have been analyzing spectroscopic data on diatomic molecules to be able to tell experimentalists what laser wavelengths to use to induce two cold atoms to bind together into a cold molecule. The next stage of the work is to analyze effects of nuclear spin structure (analogous to effects that are used in nuclear magnetic resonance imaging), which become predominant in certain regimes.With regard to the broader impact of this work, it can be said that the attainment of extremely low temperatures of atoms and now of diatomic molecules allows one to overcome averaging effects at normal temperatures, when a vast number of quantum levels are occupied. By selecting particles in the lowest quantum state, it is possible to obtain much more precise information on their interactions and on their behavior. It has been possible to better understand effects that occur in complicated naturally occurring systems by being able to vary the conditions imposed on the cold atoms. For example, a periodic laser light field can mimic the periodic potential in a crystalline lattice, but over a range of lattice amplitude and wavelength. This has already produced new insights into phenomena such as high temperature (above 50 Kelvin) superconductivity and also into the complicated interactions within atomic nuclei. Superconductors are now used in many reseach applications. Their use in electrical power transmission in areas of high electrical current density could improve the efficiency of the U. S. power grid.