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Cao, Wei; Laurent, Guillaume; De, Sankar; Schöffler, M. S.; Jahnke, T.; Alnaser, A. S.; Bocharova, I.; Stuck, C.; Ray, D.; Kling, Matthias F.; Ben‐Itzhak, I.; Weber, Thorsten; Landers, A. L.; Belkacem, A.; Dørner, R.; Orel, A. E.; Rescigno, T. N.; Cocke, C. L.

doi:10.1103/physreva.84.053406

Cited by 15 publications

(10 citation statements)

References 18 publications

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“…A grating-based monochromator consisting of a pair of identical holographic blazed gratings (3600 lines=mm) followed by a slit is installed after the harmonic generation cell, allowing the selection of the 11th harmonic (∼17 eV). The other part of the laser pulse energy is combined with the 11th harmonic pulse to form a MachZehnder interferometer [15]. Both the 11th harmonic pulse and the IR probe pulse are focused independently onto the gas target in a reaction microscope [16,17].…”

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Identification of a Previously Unobserved Dissociative Ionization Pathway in Time-Resolved Photospectroscopy of the Deuterium Molecule

et al. 2015

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A femtosecond vacuum ultraviolet (VUV) pulse with high spectral resolution (< 200 meV) is selected from the laser-driven high order harmonics. This ultrafast VUV pulse is synchronized with an infrared (IR) laser pulse to study dissociative ionization in deuterium molecules. At a VUV photon energy of 16.95 eV, a previously unobserved bond-breaking pathway is found in which the dissociation direction does not follow the IR polarization. We interpret it as corresponding to molecules predissociating into two separated atoms, one of which is photoionized by the following IR pulse. A time resolved study allows us to determine the lifetime of the intermediate predissociation process to be about 1 ps. Additionally, the dissociative ionization pathways show high sensitivity to the VUV photon energy. As the VUV photon energy is blueshifted to 17.45 eV, the more familiar bond-softening channel is opened to compete with the newly discovered pathway. The interpretation of different pathways is supported by the energy sharing between the electron and nuclei. DOI: 10.1103/PhysRevLett.114.113001 PACS numbers: 33.80.Rv, 33.80.Gj, 42.65.Ky The development of ultrafast laser techniques enables us to observe and steer dynamical processes in quantum systems with unprecedented time resolution. The optical pump-probe approach with femtosecond laser pulses allows monitoring of the bond-breaking processes in a chemical reaction [1,2], leading to the era of femtochemistry. The discovery of high order harmonics and their application for ultrafast EUV pulse generation has extended our time-resolved tools to the subfemtosecond scale, resulting in the birth of attosecond science [3][4][5]. The development of shorter light bursts is essential to capturing ultrafast motion in the microscopic world.On the other hand, in spectroscopic studies high energy resolution synchrotron radiation has been regularly used to probe atoms and molecules, and the energy structure of the corresponding quantum system can be deduced from the absorption spectra. Although the two aspects of a quantum system, namely time evolution and energy structure, are both of great importance, their relationship is governed by the uncertainty principle. The precise determination of time is accompanied by downgrading the precision of the energy information, and vice versa. Thus, an outstanding question is: Is it necessary to treat the time and energy resolution on equal footing in order to gain more comprehensive or new information of a physical process?In this Letter we take the prototypical fragmentation process, the light-induced dissociative ionization (DI) of a deuterium molecule, as an example. During the bondbreaking process, photons absorbed by the molecule break it apart into a deuteron, a photoelectron and a deuterium atom, leaving the system in the double continuum, where both the electron and nuclei are in the continuum. The more massive hydrogen isotope D 2 is used because the ionic fragment D þ can be separated from the background H þ , providing experimental da...

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Identification of a Previously Unobserved Dissociative Ionization Pathway in Time-Resolved Photospectroscopy of the Deuterium Molecule

et al. 2015

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“…The rapid development of laser technology, ultrashort vacuum ultraviolet (VUV), and extreme ultraviolet (XUV) sources in combination with advanced detection techniques, such as momentum imaging spectroscopy, has opened new opportunities for unraveling and controlling ultrafast molecular dynamics of nonequilibrium systems [1][2][3][4][5][6][7]. Recent studies showed how femtosecond VUV and XUV radiation can be used to reveal transient nuclear and electron dynamics in diatomic molecules [8][9][10][11][12] as well as in more complex molecular systems [13,14].…”

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Mapping and controlling ultrafast dynamics of highly excited H2 molecules by VUV-IR pump-probe schemes

et al. 2017

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We used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H 2 molecules. A nuclear wave packet is created in the B 1 + u state of the neutral H 2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B 1 + u electronic state, the effective H 2 + ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H 2 *, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.

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“…Importantly, the attosecond to few-femtosecond nature of the HHG radiation forms a temporally localized excited state wavepacket whose dynamics can be followed in real-time using a time-delayed probe [5][6][7][8][9]. Recently experiments have employed these attosecond XUV sources to study ultrafast fragmentation [10] and autoionization [11,12] in highly excited molecular ions.…”

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Ultrafast Dynamics of Neutral Superexcited Oxygen: A Direct Measurement of the Competition between Autoionization and Predissociation

2012

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Using ultrafast extreme ultraviolet pulses, we performed a direct measurement of the relaxation dynamics of neutral superexcited states corresponding to the nlσg(c 4 Σ − u ) Rydberg series of O2. An XUV attosecond pulse train was used to create a temporally localized Rydberg wavepacket and the ensuing electronic and nuclear dynamics were probed using a time-delayed femtosecond nearinfrared pulse. We investigated the competing predissociation and autoionization mechanisms in superexcited molecules and found that autoionization is dominant for the low n Rydberg states. We measured an autoionization lifetime of 92±6 fs and 180±10 fs for (5s, 4d)σg and (6s, 5d)σg Rydberg state groups respectively. We also determine that the disputed neutral dissociation lifetime for the ν = 0 vibrational level of the Rydberg series is 1100 ± 100 fs.

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Dynamic modification of the fragmentation of autoionizing states of O2+

Cited by 15 publications

References 18 publications

Identification of a Previously Unobserved Dissociative Ionization Pathway in Time-Resolved Photospectroscopy of the Deuterium Molecule

Identification of a Previously Unobserved Dissociative Ionization Pathway in Time-Resolved Photospectroscopy of the Deuterium Molecule

Mapping and controlling ultrafast dynamics of highly excited H2 molecules by VUV-IR pump-probe schemes

Ultrafast Dynamics of Neutral Superexcited Oxygen: A Direct Measurement of the Competition between Autoionization and Predissociation

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