Rescattering Double Ionization ofD2andH2by Intense Laser Pulses

Abstract

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.

Recoil-ion and electron momentum spectroscopy: reaction-microscopes

“…Expecially in laser physics, however, where only three groups world-wide have made use of Reaction Microscopes until now, a whole bunch of investigations might become feasiable: Among them are differential (see e.g. Hasegawa et al (2001);Yamanouchi (2002)) as well as kinematically complete measurements on molecules (a first one has been reported recently by Rottke et al (2002), see also Staudte et al (2002), Alnaser et al (2003)), on state-prepared molecular ions or experiments allowing to extract fully differential cross sections as routinely done for photon, electron or ion impact.…”

Real-time observation of vibrational revival in the fastest molecular system

“…Thus, the dream of following in real-time and with high-resolution ro-vibrational molecular motion and the possible coupling between the nuclear degrees of freedom as well as between the nuclei and the electrons, beyond the Born-Oppenheimer approximation, is deeming at the horizon. proton is shown, and not the total kinetic energy release, as, for example, in [18,19,22]. …”

“…Thus, for example, the vibrational motion in H 2 + occurs on a time scale of about 10 fs that is even nowadays not reachable with commercial laser systems. Using longer pulses, an alternative approach based on the so called 'molecular clock' concept has been suggested [16][17][18][19] delivering time-resolved information as well. Here, the removal of one electron by the laser pulse starts the clock, launching both a continuum electronic and a bound nuclear wave packet, respectively.…”

Isotope Effect in Tunneling Ionization of Neutral Hydrogen Molecules

“…The two isotopes have exactly the same electronic states and potential energy curves, the only difference is the nuclear mass, which can lead to different nuclear wavefunctions and different nuclear dynamics in the ionization process. While nuclear mass effects have been observed in many strong-field experiments, such as the multiphoton ionization [5], HHG [3,6], the laser-induced coherent nuclear motion [7], CEP-dependent asymmetry of dissociation [8], and rescattering double ionization [9,10], so far there was no experimental verification of isotope effect on total molecular ionization rate as predicted by TWM. Here we verify this prediction by comparing single ionization yields of 2 and 2 under identical conditions.…”

“…Secondly, circular polarization minimizes possible effect of molecular alignment during the pulse, which was also checked by comparing angular distributions for proton and deuteron dissociation fragments. Thirdly, and most importantly, circular polarization supresses recollisioninduced production of high-energy protons and deuterons [10], whose kinetic energy is overlapped with the double ionization channel. Since we only detect charged particles, the dissociation and double ionization contribute differently to the total proton/deuteron count.…”