Abstract Response of the wave packet of a one-dimensional Coulomb atom to an intense laser field is calculated using the symmetrized split operator fast Fourier method. The high-order harmonic generation (HHG) of the initial state separately being the ground and excited states is presented. When the hardness parameter $\alpha$ in the soft Coulomb potential $V(x)=-1/\sqrt{x^2+\alpha}$ is chosen to be small enough, the so-called hard Coulomb potential $V(x)=-1/|x|$ can be obtained. It is well known that the hard one-dimensional Coulomb atom has an unstable ground state with an energy eigenvalue of $\sim0.5$ and it has no states corresponding to physical states in the true atoms, and has the first and second excited states being degenerate. The parity effects on the HHG can be seen from the first and second excited states of the hard one-dimensional Coulomb atom. The HHG spectra of the excited states from both the soft and hard Coulomb atom models are shown to have more complex structures and to be much stronger than the corresponding HHG spectrum of the ground state of the soft Coulomb model with $\alpha=2$ in the same laser field. Laser-induced non-resonant one-photon emission is also observed.
Received: 23 June 2006
Revised: 08 July 2006
Accepted manuscript online:
(Frequency conversion; harmonic generation, including higher-order harmonic generation)
Fund: Project supported by the
National Natural Science Foundation of China (Grant No~10474138)
and the National High-Tech Inertial Confinement
Fusion Committee in China.
Cite this article:
Zhou Zhao-Yan(周兆姸） and Yuan Jian-Min(袁建民) High-order harmonic generation spectrum of an excited one-dimensional Coulomb atom in an intense laser field 2007 Chinese Physics 16 675
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