N2+2离子在线偏振和圆偏振强激光场中的解离

基于N+离子的飞行时间质谱, 研究了N2+2离子在线偏振和圆偏振强飞秒激光场中(45 fs, 5×1015-1×1016 W·cm-2, 800 nm)的解离. 通过对N+离子质谱和平动能的分析发现, N2+2离子在线偏振光和圆偏振光作用下具有不同的解离方式. 在线偏振光下, N2分子在平衡核间距RE处发生次序双电离生成N2+2离子, N2+2离子解离所释放的能量能够用单光子跃迁模型来解释. 而在圆偏振光下, N2分子首先电离生成N+2离子, N+2离子在核间距增大到临界核间距RC(>RE)时, 进一步被电离从而发生解离, 此时解离所释放的能量可以用库仑推斥模型来解释.

Dissociation of N22+in Intense Linearly and Circularly Polarized Laser Fields

The dissociation of N2+2 in intense linearly polarized and circularly polarized femtosecond laser fields (45 fs, 5×1015-1×1016 W·cm-2) is studied at a laser wavelength of 800 nm and the experiment is based on time-of-flight (TOF) mass spectra of N+ fragment ions. By analyzing TOF mass spectra and the kinetic energy of N+ ions, we found that the dissociation mechanism of N2+2 in linearly polarized laser fields is different from that in circularly polarized laser fields. In linearly polarized laser fields, N2+2 ions are formed at the equilibrium separation RE of N2 molecules by sequential ionization and the kinetic energy release of the dissociation channel is consistent with predictions of the one-photon-absorption model. In circularly polarized laser fields, N2 molecules are ionized to N+2 ions first and then two atomic cores of N+2 ions start to separate from each other. When the internuclear separation reaches the critical separation RC (>RE), a dissociation occurs after the N+2 ion loses an electron. The kinetic energy release of the dissociation channel can be interpreted by Coulomb repulsion model.