Rydberg Atom-Microwave Interactions

里德伯原子-微波相互作用

• 批准号: 1206183
• 负责人: Thomas Gallagher
• 金额: $ 44.98万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206183&HistoricalAwards=false
• 关键词: Rydberg; Atom; Microwave; Interactions

The authors are conducting a research program in which they are studying highly excited, or Rydberg, atoms in strong microwave fields. They have two specific goals. The first is to understand novel states of the combined atom-field system which are remarkably stable, even at energies above the ionization limit of the atom, the energy above which the valence electron is normally not bound to the atom. The atom is stabilized by the combination of the Coulomb field and an oscillating field with a frequency far in excess of the intrinsic frequency of the valence electron's orbit. The second goal of the project is to manipulate the Rydberg atoms with weak microwave fields oscillating at frequencies close to the orbital frequencies of the atoms. In classical terms the motion of the valence electron is phase locked to a microwave field, which is then varied to alter the electron's orbit in the same way.These experiments are carried out using an atomic beam of lithium atoms, which are excited to energies near the ionization limit, either to Rydberg states just below the limit or to energies just above it. The excitation is done using a 1 kiloHertz repetition rate laser system, and the excited atoms are exposed to the microwave pulse either during or after laser excitation. The effect of the microwave field is analyzed in one of three ways. After the end of the microwave pulse the final states are analyzed by selective field ionization, which reveals the energy distribution of bound final states. During the microwave pulse the atoms are exposed to a temporally short, 1 picosecond, field pulse which gives the electrons a momentum kick and ionizes the atoms if the electron is moving in the direction of the momentum kick. Finally, during the microwave pulse the atoms are exposed to a phase locked harmonic of the microwave field, which, with the proper phase, ionizes atoms with orbits phase locked to the microwave field. The latter two techniques enable the authors to determine the electron's time resolved velocity.The intellectual merit of the proposed activity is twofold. First, it promises to lead to new insights into the importance of the often ignored Coulomb potential in the presence of strong radiation fields. Specifically, it will clarify how the combination of the Coulomb potential and a strong radiation field can together produce unexpected effects. Second, the Rydberg atom-microwave system is one in which the presence of multiple levels on coherent population transfer can be studied in a quantitative fashion.The authors expect their work to have broad impact beyond their own interests. Insights into strong field physics are immediately transferrable to high intensity laser physics. The techniques used in the manipulation of Rydberg atoms, such as coherent population transfer, can be generalized and used in other contexts and are of particular interest in physical chemistry. More generally, manipulation of Rydberg atoms is of interest for the production of low lying states of antihydrogen, quantum computing, axion searches, and long wavelength photon detection.

作者正在进行一项研究计划，研究强微波场中的高激发原子或里德伯原子。他们有两个具体目标。首先是了解组合原子场系统的新状态，即使在高于原子电离极限的能量下，该系统也非常稳定，在该能量之上，价电子通常不会与原子结合。 库仑场和振荡场的组合使原子稳定，振荡场的频率远远超过价电子轨道的固有频率。该项目的第二个目标是利用以接近原子轨道频率振荡的微弱微波场来操纵里德伯原子。用经典术语来说，价电子的运动被锁相到微波场，然后改变微波场以同样的方式改变电子的轨道。这些实验是使用锂原子的原子束进行的，锂原子被激发到接近电离极限的能量，要么激发到略低于该极限的里德伯态，要么激发到略高于该极限的能量。激发是使用 1 kHz 重复率激光系统完成的，激发的原子在激光激发期间或之后暴露于微波脉冲。微波场的影响可以通过三种方式之一进行分析。微波脉冲结束后，通过选择性场电离分析最终态，揭示了束缚最终态的能量分布。在微波脉冲期间，原子暴露于短暂的 1 皮秒场脉冲，该脉冲给予电子动量冲击，如果电子沿动量冲击方向移动，则使原子电离。最后，在微波脉冲期间，原子暴露于微波场的锁相谐波中，该谐波具有适当的相位，电离轨道锁相到微波场的原子。后两种技术使作者能够确定电子的时间分辨速度。所提出的活动的智力价值是双重的。首先，它有望让人们对强辐射场中经常被忽视的库仑势的重要性产生新的认识。 具体来说，它将阐明库仑势和强辐射场的组合如何共同产生意想不到的效果。 其次，里德堡原子微波系统是一个可以以定量方式研究相干布居迁移的多个水平的存在的系统。作者期望他们的工作能够产生超出他们自己兴趣的广泛影响。对强场物理学的见解可以立即转移到高强度激光物理学中。 用于操纵里德伯原子的技术，例如相干布居转移，可以推广并用于其他情况，并且在物理化学中特别令人感兴趣。 更一般地说，里德伯原子的操纵对于反氢低位态的产生、量子计算、轴子搜索和长波长光子探测很有意义。