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X M Tong

Publications and source records attributed to X M Tong.

6 recordsLinked to original sources
PubMed2004

Routes to control of H2 Coulomb explosion in few-cycle laser pulses.

We have measured coincident ion pairs produced in the Coulomb explosion of H2 by 8-30 fs laser pulses at different laser intensities. We show how the Coulomb explosion of H2 can be experimentally controlled by tuning the appropriate pulse duration and laser intensity. For laser pulses less than 15 fs, we found that the rescattering-induced Coulomb explosion is dominated by first-return recollisions, while for longer pulses and at the proper laser intensity, the third return can be made to be the major one. Additionally, by choosing suitable pulse duration and laser intensity, we show H2 Coulomb explosion proceeding through three distinct processes that are simultaneously observable, each exhibiting different characteristics and revealing distinctive time information about the H2 evolution in the laser pulse.

Journal Article↗
PubMed2004

Propensity rule for novel selective double photoexcitation of helium atoms in strong static electric fields.

We studied the double photoexcitation spectra of helium in a strong dc electric field and compared the results with the recent experimental data of Harries et al. [Phys. Rev. Lett. 90, 133002 (2003)]]. We derived the propensity rules based on the crossing or noncrossing of energies in the Stark map to predict the selective subset of doubly excited states that are preferentially populated in such experiments. It is shown that the propensity rule is a consequence of the ubiquitous correlation properties of doubly excited states in general.

Journal Article↗
PubMed2003

Probing molecular dynamics at attosecond resolution with femtosecond laser pulses.

The kinetic energy distribution of D+ ions resulting from the interaction of a femtosecond laser pulse with D2 molecules is calculated based on the rescattering model. From analyzing the molecular dynamics, it is shown that the recollision time between the ionized electron and the D+2 ion can be read from the D+ kinetic energy peaks to attosecond accuracy. We further suggest that a more precise reading of the clock can be achieved by using shorter fs laser pulses (about 15 fs).

Journal Article↗
PubMed2003

Rescattering double ionization of D2 and H2 by intense laser pulses.

We have measured momentum spectra and branching ratios of charged ionic fragments emitted in the double ionization of D2 (and H2) molecules by short intense laser pulses. We find high-energy coincident D+ (and H+) ion pairs with kinetic energy releases between 8 and 19 eV which appear for linearly polarized light but are absent for circularly polarized light. The dependence on the polarization, the energy distributions of the ions, and the dependence on laser intensity of yield ratios lead us to interpret these ion pairs as due to a rescattering mechanism for the double ionization. A quantitative model is presented which accounts for the major features of the data.

Journal Article↗