Excited neutral atomic fragments in the strong-field dissociation of N<sub>2</sub>molecules

Nubbemeyer, Thomas; Eichmann, U.; Sandner, W.

doi:10.1088/0953-4075/42/13/134010

Cited by 55 publications

(39 citation statements)

References 18 publications

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“…Before summarizing, we reflect on the possible principal quantum number, n, of the Rydberg states produced by FTI. Simulations for He [22] suggest an n distribution peaked around n = 8 and dropping off rapidly for higher n. Experiments on N 2 [25] attempted to directly measure the n distribution and found that states with n > 45 are hardly populated, those with 23 < n < 45 make up over 50% of the population, and those with n < 23 the remainder. The authors also noted that atoms with n 15 were likely to have decayed in their experiments and may not have been recorded.…”

Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

“…Nevertheless, it is important to bear in mind that in our spectrometer setup we applied a static electric field of strength 400 V cm −1 for both the 7 and 40 fs experiments-sufficient to field ionize high-lying Rydberg states. From the saddle point field strength relation, F sad = 1 16n 4 , relating the applied field strength to the lowest n state that can be field-ionized [25], we estimate that only neutral fragments with n 30 would have survived without being field-ionized by our spectrometer. This number is a little higher, n 35, if instead one uses the diabatic field ionization formula, F = 1 9n 4 [25].…”

Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

“…From the saddle point field strength relation, F sad = 1 16n 4 , relating the applied field strength to the lowest n state that can be field-ionized [25], we estimate that only neutral fragments with n 30 would have survived without being field-ionized by our spectrometer. This number is a little higher, n 35, if instead one uses the diabatic field ionization formula, F = 1 9n 4 [25]. Our experiments are, however, fortunate not to suffer from a limitation on the lowest n state that may be detected as the neutral fragments are moving with high energy in the laboratory frame.…”

Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

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Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

et al. 2012

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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,

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Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

Section: Limit On Rydberg States Detectedmentioning

confidence: 99%

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Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

et al. 2012

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“…Since the first report of FTI in atoms, Manschwetus et al have observed the formation of excited H * atoms following strong-field laser fragmentation of H 2 [21] (see also N 2 [22], Ar 2 [23,24], and theory for D 3 + [25]). In conjunction with these experiments, we have performed measurements of excited D * atoms from D 2 that we report here.…”

Section: Introductionmentioning

confidence: 99%

Frustrated tunneling ionization during laser-induced D2fragmentation: Detection of excited metastable D*atoms

et al. 2011

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In a recent Letter, Manschwetus et al. [Phys. Rev. Lett. 102, 113002 (2009)] reported evidence of electron recapture during strong-field fragmentation of H 2 -explained using a frustrated tunneling ionization model. Unusually, the signature of this process was detection of excited H * atoms. We report here an extensive study of this process in D 2 . Our measurements encompass a study of the pulse duration, intensity, ellipticity, and angular distribution dependence of D * formation. While we find that the mechanism suggested by Manschwetus et al. is consistent with our experimental data, our theoretical work shows that electron recollision excitation cannot be completely ruled out as an alternative mechanism for D * production.

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

2014

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We study the formation of highly excited neutral atoms during the break-up of strongly-driven molecules. Past work on this significant phenomenon has shown that during the formation of highly excited neutral atoms (H * ) during the break-up of H2 in a linear laser field the electron that escapes does so either very quickly or after remaining bound for a few periods of the laser field. Here, we address the electron-nuclear dynamics in H * formation in elliptical laser fields, through Coulomb explosion. We show that with increasing ellipticity two-electron effects are effectively "switchedoff". We perform these studies using a toolkit we have developed for semiclassical computations for strongly-driven multi-center molecules. This toolkit includes the formulation of the probabilities of strong-field phenomena in a transparent way. This allows us to identify the shortcomings of currently used initial phase space distributions for the electronic degrees of freedom. In addition, it includes a 3-dimensional method for time-propagation that fully accounts for the Coulomb singularity. This technique has been previously developed in the context of celestial mechanics and we currently adopt it to strongly-driven systems. Moreover, we allow for tunneling during the time-propagation. We find that this is necessary in order to accurately describe the fragmentation of strongly-driven molecules.

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Excited neutral atomic fragments in the strong-field dissociation of N₂molecules

Cited by 55 publications

References 18 publications

Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

Frustrated tunneling ionization during laser-induced D2fragmentation: Detection of excited metastable D*atoms

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

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Excited neutral atomic fragments in the strong-field dissociation of N2molecules

Cited by 55 publications

References 18 publications

Frustrated tunnelling ionization during strong-field fragmentation of D3+

Frustrated tunnelling ionization during strong-field fragmentation of D3+

Frustrated tunneling ionization during laser-induced D2fragmentation: Detection of excited metastable D*atoms

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

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Excited neutral atomic fragments in the strong-field dissociation of N₂molecules

Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺

Frustrated tunnelling ionization during strong-field fragmentation of D₃⁺