论文标题
富勒烯-C60中封装的Ortho和Para水的旋转相干性
Rotational Coherence of Encapsulated Ortho and Para Water in Fullerene-C60
论文作者
论文摘要
通过化学手术在富勒烯-C60中封装单个水分子为研究低温温度下的水自旋异构体的独特旋转动力学提供了独特的机会。在这里，我们采用单周期Terahertz（THZ）脉冲来连贯地激发富勒烯-C60中孔和para水的低频旋转运动。 THZ脉冲沿沿场极化的水电偶极矩稍微定向，导致电磁波的随后发射，我们通过无场电磁采样技术解决。在高于约100 K的温度下，其笼子中的水旋转被阻尼，并且未解决发射。在较低的温度下，水旋转会产生较长的连贯衰减时间，从而在初始激发后可以观察到相干发射10-15 ps。我们观察到冷却至4 K后的发射模式的实时变化，对应于10小时内矫正水转换为para水的混合物。
Encapsulation of a single water molecule in fullerene-C60 via chemical surgery provides a unique opportunity to study the distinct rotational dynamics of the water spin isomers at cryogenic temperatures. Here, we employ single-cycle terahertz (THz) pulses to coherently excite the low-frequency rotational motion of ortho- and para-water, encapsulated in fullerene-C60. The THz pulse slightly orients the water electric dipole moments along the field polarization leading to the subsequent emission of electromagnetic waves, which we resolve via the field-free electro-optic sampling technique. At temperatures above ~100 K, the rotation of water in its cage is overdamped and no emission is resolved. At lower temperatures, the water rotation gains a long coherence decay time, allowing observation of the coherent emission for 10-15 ps after the initial excitation. We observe the real-time change of the emission pattern after cooling to 4 K, corresponding to the conversion of a mixture of ortho-water to para-water over the course of 10 hours.
