Rydberg Atom-Microwave Interactions

作者正在进行一项研究计划，在该计划中，他们正在研究强微波场中的高激发或里德伯原子。他们有两个具体目标。第一个是理解原子-场组合系统的新态，这些新态即使在高于原子电离极限的能量下也是非常稳定的，高于电离极限的能量，价电子通常不会与原子结合。 原子的稳定是由库仑场和一个频率远远超过价电子轨道固有频率的振荡场的组合所决定的。该项目的第二个目标是用弱微波场操纵里德堡原子，微波场的振荡频率接近原子的轨道频率。在经典术语中，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，锂原子被激发到电离极限附近的能量，或者到刚好低于极限的里德伯态，或者到刚好高于极限的能量。使用1千赫兹重复率激光系统进行激发，并且激发的原子在激光激发期间或之后暴露于微波脉冲。微波场的影响分析在三种方式之一。在微波脉冲结束后，利用选择性场电离分析了束缚末态，揭示了束缚末态的能量分布。在微波脉冲期间，原子暴露于时间上短的1皮秒场脉冲，该场脉冲给电子动量反冲并且如果电子在动量反冲的方向上移动则使原子电离。最后，在微波脉冲期间，原子暴露于微波场的相位锁定谐波，其具有适当的相位，电离具有相位锁定到微波场的轨道的原子。后两种技术使作者能够确定电子的时间分辨速度。首先，它有望导致新的见解的重要性，往往被忽视的库仑势在强辐射场的存在。 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。 第二，Rydberg原子-微波系统是一个可以定量研究多能级相干布居转移的系统，作者希望他们的工作能产生超出自己兴趣的广泛影响。对强场物理学的理解可以立即转移到高强度激光物理学中。 在里德伯原子的操作中使用的技术，如相干布居转移，可以推广和用于其他情况下，在物理化学中特别感兴趣。 更一般地说，里德伯原子的操纵对于反氢原子的低位态的产生、量子计算、轴子搜索和长波长光子探测都很有意义。

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.