Molecular bond stabilization in the strong-field dissociation of O2+

Abstract

We theoretically examine the rotational and vibrational dynamics of O + 2 molecular ions exposed to intense, short laser pulses for conditions realized in contemporary pump-probe experiments. We solve the time-dependent Schrödinger equation within the Born-Oppenheimer approximation for an initial distribution of randomly aligned molecular ions. For fixed peak intensities, our numerical results show that total, angle-integrated O + 2 → O( 3 P) + O + ( 4 S 0 ) dissociation yields do not monotonically increase with increasing infrared-probe pulse duration. We find this pulse-durationdependent stabilization to be consistent with the transient trapping of nuclear probability density in a light-induced (bond-hardening) potential-energy surface and robust against rotational excitation. We analyze this stabilization effect and its underlying bond-hardening mechanism (i) in the time domain, by following the evolution of partial nuclear probability densities associated with the dipolecoupled O + 2 (a 4 Πu) and O + 2 (f 4 Πg) cationic states, and (ii) in the frequency domain, by examining ro-vibrational quantum-beat spectra for the evolution of the partial nuclear probability densities associated with these states. Our analysis reveals the characteristic timescale for the bond-hardening mechanism in O + 2 and explains the onset of bond stabilization for sufficiently long pulse durations.

Directly revealing the geometric phase effect of dissociative D2+by two-color strong field photodissociation

“…In contrast to the fixed properties of natural CIs, the precise position and underlying nonadiabatic coupling strength of LICIs are determined by the incident laser frequency and intensity. 19,20,[26][27][28][29][30] This opens a new challenging area of research in manipulating nonadiabatic dynamics in molecules by intense pulses. [31][32][33][34] Recent experiments on the dissociation of H 2 + reported that the signature of light-induced potentials can be understood as modulations in photofragment momentum distributions (PMDs).…”

Disentangle pathways in strong field molecular photoionization byangular distribution of dissociation fragments

“…The photoionization and dissociation of molecules induced by intense femtosecond laser pulse are fundamental physical processes of light-matter interactions. The dissociation dynamics can be resolved in detail by delayed ultrashort probe laser pulses for a series of delays between the pump and probe laser pulses, where the pump pulse excites or ionizes the molecule and initiates the dissociation [1][2][3]. Although the ionization and dissociation of few-electron molecules, such as H 2 , have been exhaustively studied [4][5][6][7][8][9][10][11][12][13][14][15][16], the strong field ionization and subsequent dynamics of many-electron molecules do not have a coherent and comprehensive characterization of the underlying physical processes due to the complexity of the involved electronic and nuclear degrees of freedom.…”

Characterization of light-induced potentials in the strong-field dissociation of O2+

“…The dissociation of molecules by intense, short laser pulses is a fundamental physical light-matter-interaction process. In many cases, notably for diatomic molecules, the dissociation dynamics can be resolved in time by repeatedly exciting (and possibly ionizing) molecules in ultrashort pump-laser pulses and destructively imaging the excited nuclear dynamics with delayed ultrashort probe-laser pulses for a series of delays between the pump-and probe-laser pulses (see, e.g., [1][2][3] and references therein). A prototypical and the most elementary example is given by the femtosecond time-resolved imaging of the bound and dissociative nuclear dynamics in H 2 + (or D 2 + ) molecular ions in pump-probe experiments by measuring and analyzing fragment kinetic-energy-release (KER) spectra [4][5][6].…”

“…+ have been extended to model the coupled rotational and vibrational nuclear motion by solving the TDSE in two dimensions, R and the molecular alignment angle θ relative to the laser-polarization direction [3,[11][12][13]. For the dissociation of diatomic molecules, two-dimensional TDSE calculations remain computationally as well as conceptually tractable and therefore allow for a detailed study of the rovibrational light-induced dynamics during the dissociation process.…”

“…In general, for heavier diatomic molecules, the pump pulse generates coherent nuclear wave packets that simultaneously evolve on different potential energy surfaces, where they are candidates for dipole coupling in the probe-(and possibly also pump-) laser electric field to a variety of adiabatic molecular electronic states. Nevertheless, nuclear excitation and dissociation pathways have recently been distinguished in experimental and theoretical studies on N 2 [22,23], O 2 [1][2][3]10,[22][23][24], CO [22,23], and noble-gas dimers [25,26] for IR-IR [10,22,23,25,26], extreme ultraviolet (XUV)-IR [1,2], XUV-XUV [24], and IR-soft-x-ray [27] pump-probe-pulse combinations. For O 2 , in particular, the experiment performed by De et al [23] with intense few-cycle 800-nm pump-and probe-laser pulses revealed pronounced oscillations of the O + fragment yield as a function of the fragment kinetic energy at KER values below 0. g state only slightly improves the agreement with experimental KER spectra, as compared with Ref.…”