超冷态到准经典态光解离过渡的实验和理论研究
Experimental and Theoretical Investigation of the Crossover from the Ultracold to the Quasiclassical Regime of Photodissociation
摘要：
在超低能量下，原子和分子经历碰撞和反应，这些最好用量子机械波函数来描述。相反，在更高的能量下，这些过程可以被准经典地理解。在这里，我们从实验和理论上研究了超冷双原子锶分子光解离从量子力学到准经典体系的交叉。这种基本反应是在完全控制分子及其光致碎片的量子态的情况下进行的。的photorfragment角分布成像，并计算使用量子力学模型以及WKB和半经典近似，明确地比较在一个范围内的photorfragment能量。的反应过程中收敛到其高能量（轴向反冲）的限制时，能量超过任何反应障碍的高度。这种现象是定量研究双通道光解使用直观的参数通道振幅和相位。虽然轴向反冲极限通常被发现是很好地描述了一个常用的准经典模型，我们发现，当光碎片是相同的粒子，它们的玻色子或费米子量子统计可能会导致这个模型失败，需要量子力学处理，即使在高能量。
英文摘要：
At ultralow energies, atoms and molecules undergo collisions and reactions that are best described in terms of quantum mechanical wave functions. In contrast, at higher energies these processes can be understood quasiclassically. Here, we investigate the crossover from the quantum mechanical to the quasiclassical regime both experimentally and theoretically for photodissociation of ultracold diatomic strontium molecules. This basic reaction is carried out with a full control of quantum states for the molecules and their photofragments. The photofragment angular distributions are imaged, and calculated using a quantum mechanical model as well as the WKB and a semiclassical approximation that are explicitly compared across a range of photofragment energies. The reaction process is shown to converge to its high-energy (axial recoil) limit when the energy exceeds the height of any reaction barriers. This phenomenon is quantitatively investigated for two-channel photodissociation using intuitive parameters for the channel amplitude and phase. While the axial recoil limit is generally found to be well described by a commonly used quasiclassical model, we find that when the photofragments are identical particles, their bosonic or fermionic quantum statistics can cause this model to fail, requiring a quantum mechanical treatment even at high energies.
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