Multiple Recapture of Electrons in Multiple Ionization of the Argon Dimer by a Strong Laser Field

Abstract

We observe multiply frustrated tunneling ionization-induced dissociation of the argon dimers by intense linearly polarized ultrashort laser pulses. By measuring the kinetic energy release and angular distribution of the Coulomb explosion of up to eightfold ionized argon dimers, we can trace the recapture of up to two electrons to Rydberg states of the highly charged compound at the end of the laser pulse. Upon dissociation of the dimer, the Rydberg electron prefers to localize at the atomic ion with the higher charge state. We probe the electron recapture dynamics by a time-delayed weak pulse.

Frustrated tunnelling ionization during strong-field fragmentation of D3+

“…Demonstrated originally in strong-field ionization of helium, Nubbemeyer et al showed that an electron wavepacket that starts to tunnel away from the core in an intense laser field, but fails to acquire sufficient drift momentum to escape the attractive potential of the remaining He + ion, can be captured into an excited Rydberg orbital of the He atom-in effect 'frustrating' the tunnel ionization process. This process must occur during the laser pulse to conserve energy and momentum, most likely during the trailing edge, as the electron is gently decelerated over many laser cycles before being pulled into orbit.The same mechanism has been observed in the dissociative ionization of a few diatomic molecules (H 2 [23], D 2 [24], O 2 [25] and Ar 2 [26][27][28]). For such molecules, following ionization, an electron that is excited to the continuum and driven by the laser field tends to be captured to a Rydberg orbital of one of the two 'Coulomb-exploding' fragment ions.…”

“…The same mechanism has been observed in the dissociative ionization of a few diatomic molecules (H 2 [23], D 2 [24], O 2 [25] and Ar 2 [26][27][28]). For such molecules, following ionization, an electron that is excited to the continuum and driven by the laser field tends to be captured to a Rydberg orbital of one of the two 'Coulomb-exploding' fragment ions.…”

“…To summarize, we have uncovered for the first time compelling experimental evidence for FTI in a polyatomic molecule-indeed, the benchmark D + 3 system. FTI, involving the capture of a continuum electron that has begun to tunnel free, has only recently been discovered as a new mechanism in atoms [22] and diatomic molecules [23][24][25][26][27][28]. We observe evidence for FTI in the three-body dissociative ionization channel of D + 3 leading to D + + D + + D, where this channel strongly resembles the Coulomb explosion channel D + + D + + D + from which FTI emerges.…”

“…The method that we have used to detect FTI is unique compared to recent measurements. Other observations of FTI [22][23][24][25][26][27][28], starting from neutral gas targets, have relied on the neutral fragments being produced in an excited state with sufficient internal energy ( 5 eV) to overcome the work function of the microchannel-plate detector, i.e. to trigger a signal.…”

Toolkit for semiclassical computations for strongly driven molecules: Frustrated ionization ofH2driven by elliptical laser fields

“…The formation of highly excited neutral fragments in linearly polarized laser fields has attracted a lot of interest in the last few years [10][11][12][13][14]. In [15] we reported a theoretical study of the mechanisms of this "frustrated"-since only one electron eventually escapes-double ionization process.…”