Enhancing High-Order Above-Threshold Dissociation of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi mathvariant="normal">H</mml:mi><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math>Beams with Few-Cycle Laser Pulses

McKenna, J. A.; Sayler, A. M.; Anis, Fatima; Gaire, B.; Johnson, Nora G.; Parke, E.; Hua, J. J.; Mashiko, Hiroki; Nakamura, Christopher M.; Moon, Eric; Chang, Zenghu; Carnes, K. D.; Esry, B. D.; Ben‐Itzhak, I.

doi:10.1103/physrevlett.100.133001

Cited by 87 publications

(72 citation statements)

References 28 publications

(28 reference statements)

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“…In the higher KER range (1.65 -1.9 eV), the asymmetry likely arises from an interference of 1-photon BS and net 2-photon ATD [46]. The vibrational levels v=5 -8 meet the requirements for generating an asymmetry in this region, [see pink-shaded section of Fig.…”

Section: Pacs Numbers: XXXmentioning

confidence: 99%

Carrier-Envelope Phase Control over Pathway Interference in Strong-Field Dissociation ofH2+

et al. 2013

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The dissociation of an H + 2 molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4×10 14 W/cm 2 with a central wavelength of 730 nm was studied using a coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction of H + fragments relative to the laser polarization were observed. These asymmetries are caused by interference of odd and even photon number pathways, where net-zero photon and 1-photon interference predominantly contributes at H + +H kinetic energy releases of 0.2 -0.45 eV, and net-2-photon and 1-photon interference contributes at 1.65 -1.9 eV. These measurements of the benchmark H + 2 molecule offer the distinct advantage that they can be quantitatively compared with ab initio theory to confirm our understanding of strong-field coherent control via the carrier-envelope phase. PACS numbers: XXXOne ultimate goal of ultrafast, strong-field laser science is to coherently control chemical reactions [1][2][3]. A prerequisite to achieving this goal is to understand the control mechanisms and reaction pathways. To this end, tailoring the electric field waveform of few-cycle laser pulses to control reactions and uncover the underlying physics has become a powerful tool [4][5][6]. It has been applied to the dissociative ionization of H 2 and its isotopologues [7][8][9][10][11][12] and has recently been extended to more complex diatomic molecules, such as CO [13][14][15], and to small polyatomic molecules [16,17].Conceptually, one of the most basic features of a fewcycle laser pulse to control is the carrier-envelope phase (CEP). When the laser's electric field is written as E(t) = E 0 (t) cos(ωt + φ), E 0 (t) is an envelope function, ω is the carrier angular frequency, and φ is the CEP. In fact, all of the few-cycle waveform experiments cited above used the CEP as the control parameter.For example, Kling et al. used 5 fs, 1.2×10 14 W/cm 2 pulses with stabilized CEP to dissociatively ionize D 2 and found asymmetries in the emission direction of D + ions for kinetic energy releases (KER) above 6 eV [7,8]. The diminished dissociation signal in a circularly polarized laser field indicated that recollision played a role. Recollision entails a tunnel-ionized electron undergoing a collision with its parent ion after acceleration by the oscillating laser field [18,19]. The energy exchange between the laser-driven electron and the parent ion can promote the D + 2 to the 2pσ u excited state. Coupling of the 2pσ u and 1sσ g states [20] on the trailing edge of the laser pulse during the dissociation of D + 2 was suggested as the explanation for the CEP-dependent asymmetry [7,8].Another example comes from Kremer et al. who exposed an H 2 target to 6 fs, 4.4×10 14 W/cm 2 CEPstabilized laser pulses and observed asymmetries for KER values between 0.4 and 3 eV [9] -energies they attributed to bond softening (BS) [21] and not electron recollision, which has higher KER. They proposed that the initial ionization of H 2 generates a coherent wav...

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Section: Pacs Numbers: XXXmentioning

confidence: 99%

Carrier-Envelope Phase Control over Pathway Interference in Strong-Field Dissociation ofH2+

et al. 2013

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“…11. The locking duration is sufficient for many low count rate experiments, such as attosecond streaking and laser ion beam interaction experiments, which can require several hours of CE phase stabilization McKenna et al, 2008). To control the CE phase in the experiment, the grating separation of the compressor was stabilized at preset values.…”

Section: Ce Stabilization Of Regenerative Amplifiermentioning

confidence: 99%

Carrier-Envelope Phase Stablization of Grating Based High-Power Ultrafast Laser

Chen¹,

Wu²,

Zhao³

et al. 2010

Coherence and Ultrashort Pulse Laser Emission

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“…For the 3-µm field, the underlying mechanism for the electron localization is found to be based on the interferences between the one-and higher-order photon coupling channels. Due to the enhanced ATD for heavier isotopes [23], the interference maxima gradually become in phase with growing nuclear mass, resulting in the anomalous isotopic effect where the electron localization degree is larger for heavier isotopes.In our simulations, we have used a numerical model that has been well established for studies of electron localization in the laser-driven molecular dissociation [8,9]. This model solves the time-dependent Schrödinger equation (TDSE) for the nuclear wavepacket in the BornOppenheimer (BO) representation.…”

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“…This is because different isotopes of a given element have a similar electronic structure and chemical properties, but different masses. Indeed, the isotopic effect has been an important issue in the research of laser-molecule interactions, such as high-harmonic generation [21], nuclear dynamics detection [22] and high-order above-threshold dissociation (ATD) [23].On the other hand, thanks to the recent advance in the generation of midinfrared source, few-cycle CEPstable pulses at 3 µm have become available in laboratory [24,25], providing a potential for controlling as well as obtaining deeper insight into the electron localization process in heavier molecules. In this Letter, we theoretically study the asymmetric dissociation of molecular hydrogen by using a few-cycle 3-µm pulse and report an anomalous isotopic effect on the electron-directed reactivity.…”

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Anomalous isotopic effect on electron-directed reactivity by a 3-μm midinfrared pulse

Liu¹,

Zhang²,

Lan³

et al. 2013

Opt. Express

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We have theoretically studied the effect of nuclear mass on electron localization in dissociating H2+ and its isotopes subjected to a few-cycle 3-µm laser pulse. Compared to the isotopic trend in the near-infrared regime, our results reveal an inverse isotopic effect in which the degree of electrondirected reactivity is even higher for heavier isotopes. With the semi-classical analysis, we find, for the first time, the pronounced electron localization is established by the interferences through different channels of one-and, more importantly, higher-order photon coupling. Interestingly, due to the enhanced high-order above-threshold dissociation of heavier isotopes, the interference maxima gradually become in phase with growing mass and ultimately lead to the anomalous isotopic behavior of the electron localization. This indicates that the multi-photon coupling channels will play an important role in controlling the dissociation of larger molecules with midinfrared pulses. PACS numbers: 33.20. Xx, 33.80.Wz, 32.80.Qk, 42.50.Hz The electronic motion inside the molecule is of fundamental importance in determining the formation and fracture of chemical bonds. For more than two decades, many efforts have been done to study the electronic dynamics in laser-matter interactions [1][2][3][4], aiming at the control over ultrafast reactions. With the recent development of laser techniques and attosecond science [5][6][7], it has become feasible to steer the electron localization in dissociating molecules with the carrier-envelope phase (CEP) stabilized few-cycle laser pulses [8][9][10][11] or the sequential ultraviolet and near-infrared pulses [12][13][14]. The asymmetric electron localization in molecules can be understood as the quantum interference of the populations that are resonantly transferred among at least two electronics states of different parity [15,16].More recently, the control of electron-directed reactivity in midinfrared laser pulses has been explored to enhance the electron localization probability via the match between the duration of the few-cycle pulse and the dissociation time of the molecule [17][18][19]. To hold the control efficiency for further heavier nuclei, one may have to use the pulse with longer wavelength [18]. While this constitutes an important step towards the control of chemical reactions in larger molecules, we are wondering whether the physical mechanism responsible for the electron localization in midinfrared pulses remains the same as that in the near-infrared regime [9]. Meanwhile, for extending the control scheme to the larger molecules, the influence of nuclear mass on the reactions must be taken into account. However, it remains unclear how the nuclear mass affects the control efficiency when the midinfrared pulses are applied, though it has been shown that the control of electron localization is weakened by the growing mass in the few-cycle near-infrared field [9,20] To understand the influence of mass in reactions, the use of isotopes is one of the practice means. This is ...

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Enhancing High-Order Above-Threshold Dissociation ofH2+Beams with Few-Cycle Laser Pulses

Cited by 87 publications

References 28 publications

Carrier-Envelope Phase Control over Pathway Interference in Strong-Field Dissociation ofH2+

Carrier-Envelope Phase Control over Pathway Interference in Strong-Field Dissociation ofH2+

Carrier-Envelope Phase Stablization of Grating Based High-Power Ultrafast Laser

Anomalous isotopic effect on electron-directed reactivity by a 3-μm midinfrared pulse

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