Asymmetric emission of high-energy electrons in the two-dimensional hydrodynamic expansion of large xenon clusters irradiated by intense laser fields
Asymmetric emission of high-energy electrons in the two-dimensional hydrodynamic expansion of large xenon clusters irradiated by intense laser fields
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DOI：
10.1103/physreva.67.043204
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发表时间：
2003-04-01
影响因子：
2.9
通讯作者：
Mathur, D
中科院分区：
文献类型：
--
作者：
Kumarappan, V;Krishnamurthy, M;Mathur, D
在持续时间在100-2200秒范围内变化的强激光脉冲(10(15)-10（16)W cm(-2)）照射下，Xe-n团簇（n=20 000-15 000）解体后发射的电子的能谱和角分布已被测量。簇爆动力学发生在水动力区。对于我们所研究的范围内较小的团簇，单电子温度充分描述了测量到的电子能量分布；在较大的簇的情况下，需要双温度拟合。当激光脉冲持续时间接近1 ps时，发现总电子发射出乎意料地不对称，并表现出共振。这些结果通过扩展流体动力学模型来合理化，该模型还考虑了光场对团簇表面诱导的极化电荷施加的力。我们发现这种电致伸缩力的大小与库仑力和水动力的大小相当，并表现出共振行为。与之前唯一的其他报告的发现相反，我们发现电子能量分布中的低能成分与团簇吸收能量的共振有关。高能成分似乎是由一种机制产生的，这种机制不受共振的强烈影响。
Energy spectra and angular distributions have been measured of electrons that are emitted upon disassembly of Xe-n clusters (n=20 000-150 000) following irradiation by intense (10(15)-10(16) W cm(-2)) laser pulses whose durations are varied over the 100-2200 fs range. The cluster explosion dynamics occur in the hydrodynamic regime. For the smaller clusters in the range that we have studied, a single-electron temperature adequately describes the measured electron energy distribution; in the case of larger clusters, a two-temperature fit becomes necessary. The total electron emission is found to be unexpectedly asymmetric and exhibits a resonance when the laser-pulse duration is similar to1 ps. These results are rationalized by extending the hydrodynamic model to also take into account the force that the light field exerts on the polarization charge that is induced on the surface of the cluster. We show that the magnitude of this electrostrictive force is comparable to those of the Coulombic and hydrodynamic forces, and it exhibits resonance behavior. Contrary to the findings of the only other earlier report, we find that the low-energy component in the electron energy distribution is connected to the resonance in energy absorption by the cluster. The high-energy component seems to be produced by a mechanism that is not so strongly influenced by the resonance.