Laser-Cooling Cadmium for Optical Atomic Clock, Cold Collisions, and Quantum Gas Experiments

该项目将开发研制以镉元素为基础的原子钟所需的实验技术。原子钟可以测量的微小频率或滴答率和短时间间隔具有广泛的应用，包括全球定位系统(GPS)、安全金融交易和美国和国际官方时间。原子钟的科学应用包括基本物理测试(如爱因斯坦的广义相对论)、测地学、长基线干涉测量和计量学。原子钟可以帮助解决诸如宇宙的基本常量(如电子质量与质子质量之比)是否随时间变化等问题。镉原子对高精度时钟的吸引力来自于使它们对来自室温环境的热辐射的破坏性影响相对不敏感的能力，这是目前许多原子钟的限制。另一个实用方面是，制造镉钟所需的激光预计比其他热敏性较小的时钟物种更可靠。镉也有各种各样的同位素(原子的8个版本，其中心有不同数量的中子)，每一种都以不同的方式相互碰撞，为制造更好的时钟提供了更多的可能性，并提供了各种有趣的基础物理研究。激光将被用来探测和控制镉原子，以便更好地理解和量化上述方面，并为更好的原子钟铺平道路。该项目将研究镉的费米子和玻色子同位素的激光冷却和捕获，特别是使用65 kHz宽326 nm的1S0-3P1跃迁。为了提高散射率以增加俘获原子的数量，预期的方法包括用350 nm的激光激发到1D2来猝灭3P1态，或者使用基于361 nm 3P2-3D3跃迁的亚稳态磁光陷阱。326 nm的1S0-3P1跃迁将在微开尔文温度下直接产生原子，这些原子可以加载到远离共振的偶极陷阱中，然后加载到魔波光学晶格中。魔术波长将被确定，镉-镉的碰撞可以在偶极陷阱中研究。更广泛地说，该项目预计将支持与世界各地的钟表组织的合作，例如，评估对国际原子时(TAI)做出贡献的初级原子钟的精度。

This project will develop experimental techniques needed to develop an atomic clock that is based on the element cadmium. The small differences in frequencies, or tick-rates, and the short time intervals that atomic clocks can measure have wide-ranging applications, including the Global Positioning System (GPS), secure financial transactions, and official U.S. and international time. Scientific applications of atomic clocks include tests of fundamental physics (such as Einstein's theory of general relativity), geodesy, long baseline interferometry, and metrology. Atomic clocks can help address questions such as whether the fundamental constants of the universe (like the ratio of the mass of an electron to the mass of a proton) change in time. The attractiveness of cadmium atoms for highly accurate clocks stems from the ability to make them relatively insensitive to the disruptive influence of thermal radiation from room-temperature surroundings, a limitation for many atomic clocks presently. An additional practical aspect is that the lasers needed to make a cadmium clock are expected to be more reliable than for other clock species with small thermal sensitivities. Cadmium also has a wide variety of isotopes (8 versions of the atom with different numbers of neutrons at its center), each of which collides with each other in different ways, opening up more possibilities to make a better clock and providing an interesting variety of fundamental physics studies. Lasers will be used to probe and control the cadmium atoms in order to better understand and quantify the aspects mentioned above and pave the way to a better atomic clock.The project will investigate laser-cooling and trapping of fermion and boson isotopes of cadmium, particularly using the 65 kHz wide 326 nm 1S0-3P1 transition. To enhance the scattering rate in order to increase the number of trapped atoms, anticipated approaches include quenching the 3P1 state with a 350 nm laser excitation to 1D2 or using a metastable magneto-optical trap based on the 361 nm 3P2-3D3 transition. The 326nm 1S0-3P1 transition will directly yield atoms at microKelvin temperatures, which can be loaded into a far off-resonance dipole trap and subsequently loaded into a magic-wavelength optical lattice. The magic wavelength will be determined and cadmium-cadmium collisions can be studied in the dipole trap. More broadly, the project is expected to support collaborations with clocks groups around the world, for example, to evaluate the accuracies of primary atomic clocks that contribute to International Atomic Time (TAI).