Benchmark measurements of H(3)(+) nonlinear dynamics in intense ultrashort laser pulses

Time-resolving the ultrafast H2 roaming chemistry and H3+ formation using extreme-ultraviolet pulses

The time scales and formation mechanisms of tri-hydrogen cation products in organic molecule ionization processes are poorly understood, despite their cardinal role in the chemistry of the interstellar medium and in other chemical systems. Using an ultrafast extreme-ultraviolet pump and time-resolved near-IR probe, combined with high-level ab initio molecular dynamics calculations, here we report unambiguously that H₃⁺ formation in double-ionization of methanol occurs on a sub 100 fs time scale, settling previous conflicting findings of strong-field Coulomb explosion experiments. Our combined experimental-computational studies suggest that ultrafast competition, between proton-transfer and long-range electron-transfer processes, determines whether the roaming neutral H₂ dynamics on the dication result in [Formula: see text] or [Formula: see text] fragments respectively.

Femtosecond Resolving Photodissociation Dynamics of the SO2 Molecule

We experimentally investigate the ultrafast photodissociation dynamics of the SO₂ molecule induced by intense ultrashort laser pulses in a pump-probe scheme. Different three-body fragmentation pathways are discriminated using the time-dependent kinetic energy release spectrum with femtosecond time resolution. A nontrivial three-body fragmentation pathway, denoted as the bonding pathway, is unraveled, in which an intermediate fast rotating O₂ molecule is formed before complete fragmentation. The ultrafast chemical bond rearrangement after electron release is tracked in real time. The bonding pathway generally exists in the three-body fragmentation processes induced by strong laser fields of different wavelengths, which is observed in infrared, ultraviolet, and mixed two-color cases. Our findings are significant for understanding the photon-induced ultrafast processes of the SO₂ molecule in atmospheric chemistry.

Ultrafast X-ray photoelectron diffraction in triatomic molecules by circularly polarized attosecond light pulses

We theoretically study ultrafast photoelectron diffraction in triatomic molecules with cyclic geometry by ultrafast circular soft X-ray attosecond pulses.

Retrieving the excitation and polarization configurations in Coulomb explosion of a trimer driven by strong laser field

Ultrafast imaging and manipulating transient molecular structures in chemical reactions and photobiological processes is a fundamental but challenging goal for scientists. Theoretically, the challenge originates from the complex multiple-time-scale correlated electron dynamics and their coupling with the nuclei. Here, we employ classical polyatomic models for this kind of study and take the Coulomb explosion of argon and neon trimers in strong laser fields as an illuminating example. Our results demonstrate that the degree of asymmetry on the kinetic energy release (KER) spectrum, together with a Dalitz plot, constitutes a powerful tool for retrieving the ionization, excitation, and polarization configurations (femtosecond-to-attosecond time-scale electron dynamics) of trimers under strong-field radiation.

Laser-induced dissociation dynamics of triatomic molecule in electronic excited states: A full-dimensional quantum mechanics study

We present a detailed theoretical approach to investigate the laser-induced dissociation dynamics of a triatomic molecule on its electronic excited state in full dimensional case. In this method, the time evolution of the time-dependent system is propagated via combined the split operator method and the expansion of Chebyshev polynomials (or short-time Chebyshev propagation) and the system wave functions are expanded in terms of molecular rotational bases. As an example of the application of this formalism, the dissociation dynamics of H3(+)→H2(+)+H induced by ultrashort UV laser pulses are investigated on new Born-Oppenheimer potential energy surfaces. Our numerical results show that the signals of dissociation products will be easier to observe as the increasing of field strength. Driving by a 266 nm laser beam, the calculated central value of kinetic-energy-release is 2.04 eV which shows excellent agreement with the experimental estimation of 2.1 eV. When the H3(+) ion is rotationally excited, the spatial distribution of product fragments will become well converged.

Duration of an intense laser pulse can determine the breakage of multiple chemical bonds

Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades. With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation. So far, all successful demonstrations in this area considered only fragmentation reactions, where only one bond is broken and the molecule is split into merely two moieties. Here, using ethylene (C2H4) as an example, we experimentally investigate whether complex fragmentation reactions that involve the breakage of more than one chemical bond can be influenced by parameters of an ultrashort intense laser pulse. We show that the dynamics of removing three electrons by strong-field ionization determines the ratio of fragmentation of the molecular trication into two respectively three moieties. We observe a relative increase of two-body fragmentations with the laser pulse duration by almost an order of magnitude. Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

Classical dynamics of laser-driven D₃⁺

A classical model of the triatomic D₃⁺ molecule subjected to an intense, few-cycle laser pulse is introduced. The model is capable of describing the laser-induced correlated motion of both electrons and nuclei in three dimensions, and allows us to follow the motion of the two electrons and three deuterons from the initial field-free state, during the pulse, and until the bond breaking into the final fragments. By averaging over many trajectories, we calculate the relative yields of the ionization and dissociation channels, as well as the kinetic energy release (KER) from the fragment ions. A comparison with recent experimental KER spectra shows good qualitative agreement. In addition, we find a pathway in which an emitted electron recombines into a high-lying Rydberg state, resulting in D + D⁺ + D⁺ fragments with the same KER as in the D⁺ + D⁺ + D⁺ channel.