Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

Abstract

We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D + 3 to D + + D + + D with 10 16 W cm −2 , 790 nm, 40 fs (and 7 fs) laser pulses. This feature strongly mimics the behaviour of the D + + D + + D + channel. From the experimental evidence, we conclude that the origin of the feature is due to frustrated tunnelling ionization, the first observation of this mechanism in a polyatomic system. Furthermore, we unravel evidence of frustrated tunnelling ionization in dissociation, both two-body breakup to D + D + 2 and D + + D 2 , and three-body breakup to D + + D + D. Gesellschaft processes involving either elastic scattering [6][7][8], inelastic scattering [9, 10], or electron-ion recombination [11]. These phenomena have led to the birth of new areas of research such as high-harmonic generation and attosecond science [12][13][14][15], laser-driven electron diffraction imaging [5][6][7][8], molecular orbital tomography [16,17] and electron wavepacket probing of molecular dynamics [18-21]-naming only a few.Related to the electron recollision process, recently Nubbemeyer et al [22] reported a new phenomenon dubbed frustrated tunnelling ionization (FTI). 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 signature of frustrated tunnelling in molecules is that, counterintuitively, the final kinetic energy release (KER) is similar to that of a Coulomb explosion event even though only one product fragment is charged while the other fragment is neutral [23].This description of FTI uses language, such as electron capture, that is usually reserved for discussions involving ionization. Throughout the paper we use this language for convenience. However, it does pose an interesting question in relation to the actual mechanism for FTI, that is,

Controlling electron-electron correlation in frustrated double ionization of triatomic molecules with orthogonally polarized two-color laser fields

“…Our previous result for the distribution of the kinetic energy release of the Coulomb exploding nuclei in FDI of D + 3 was in good agreement with experiment [7]. We employ the initial state of D [5,7]. It consists of a superposition of triangular-configuration vibrational states ν = 1 -12 [7,28].…”

“…This model has provided significant insights into FDI for strongly-driven H 2 [2] and D + 3 [8]. Our previous result for the distribution of the kinetic energy release of the Coulomb exploding nuclei in FDI of D + 3 was in good agreement with experiment [7]. We employ the initial state of D [5,7].…”

Frustrated double and single ionization in a two-electron triatomic molecule H+3

“…Incorporating tunneling during propagation in our model allows for a better description of frustrated tunnel ionization compared to the description provided by other classical models for strongly-driven triatomic molecules [20,21]. In [22], we study the kinetic energy release of the nuclei for DI and FDI for strongly-driven D [23]. We find our results in good agreement with experiment.…”

Elucidating isotopic effects in intense ultrafast laser-driven D2H+fragmentation

“…+ fragmentation 2 out, by ourselves [20,21,22,23,24] and Alexander et al [25]. Due to its basic structure, measurements of H + 3 can provide a benchmark for theory -and ultimately help develop the theoretical tools needed to explore larger systems, as exemplified by Lötstedt et al [26,27].…”