Acta Phys. -Chim. Sin. ›› 2009, Vol. 25 ›› Issue (08): 1683-1688.doi: 10.3866/PKU.WHXB20090820

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Dissociation of N2+2 in Intense Linearly and Circularly Polarized Laser Fields

ZHANG Sheng, XIA Yuan-Qin, CHEN De-Ying   

  1. National Key Laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001, P. R. China|Department of Physics, Harbin Institute of Technology, Harbin 150001, P. R. China
  • Received:2009-03-19 Revised:2009-05-07 Published:2009-07-16
  • Contact: CHEN De-Ying


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.

Key words: Dissociation, Time-of-flight mass spectrum, Intense laser field, Double ionization