Laser induced dissociation control of the symmetric diatomic molecular ion
H2+ and the triatomic molecular ion
H32+ is discussed. The simulation results demonstrate that a long-wavelength terahertz or mid-infrared laser pulse can be used to control the electrons of the dissociative states after the excitation of an ultrashort ultraviolet (UV) laser pulse. For
H2+, there exists an effective time, which increases with increasing pulse duration of the UV laser pulse, for controlling the molecular dissociation. For the electrons of the
1sσg state, they move along the polarization direction of the dissociation control electric field. In contrast, for the electrons of the
2pσu state, they move in the opposite direction to that of the electric force. And for the triatomic molecule
H32+, the electron dissociation control can also be realized by changing the central wavelength of the exciting UV pulse.
A dc electric field is utilized to steer the electron motion after the molecular ion H 2 + is excited by an ultrashort ultraviolet laser pulse. The numerical simulation shows that the electron localization distribution and the dissociation control ratio are dependent on the polarization direction and amplitude of the dc electric field. Most electrons of the dissociation state move opposite to the dc electric field and stabilize at the dressed-up potential well, for the dressed-down well is occupied by the electrons of the 1s σ g state.
Electron localization in the dissociation of the symmetric linear molecular ion H-3(2+) is investigated. The numerical simulation shows that the electron localization distribution is dependent on the central frequency and peak electric field amplitude of the external ultrashort ultraviolet laser pulse. When the electrons of the ground state are excited onto the 2p sigma(2)Sigma(+)(u) by a one-photonprocess, most electrons of the dissociation states are localized at the protons on both sides symmetrically. Almost no electron is stabilized at the middle proton due to the odd symmetry of the wave function. With the increase of the frequency of the external ultraviolet laser pulse, the electron localization ratio of the middle proton increases, for more electrons of the ground state are excited onto the higher 3p sigma(2)Sigma(+)(u) state. 50.9% electrons of all the dissociation events can be captured by the middle Coulomb potential well through optimizing the central frequency and peak electric field amplitude of the ultraviolet laser pulse. Besides, a direct current (DC) electric field can be utilized to control the electron motions of the dissociation states after the excitation of an ultraviolet laser pulse, and 68.8% electrons of the dissociation states can be controlled into the middle proton.
We present full-dimensional quantum simulations of
H2+ dissociative ionization driven by strong orthogonal laser fields. We consider equal-frequency orthogonal components, which generate elliptical or circular polarization depending on their relative phase and amplitude, as well as orthogonal
800- and
400-nm two-color fields. These two-dimensional fields strongly modify the fragmentation dynamics. Most notably, we identify a high-energy peak in the proton kinetic-energy-release (KER) spectrum at approximately
4−5 eV that is absent from the corresponding single-color, linearly polarized calculations. The yield of this peak can be coherently controlled by varying the relative carrier-envelope phase of the perpendicular field component. The perpendicular field also disrupts the clear electron-proton energy-sharing pattern observed in the main
3−3.5 eV dissociation channel, indicating more complex multichannel dynamics. Time-dependent state projections and calculations initiated from individual excited states attribute the additional peak to laser-induced vibrational excitation of
H2+. Furthermore, the perpendicular field rotates the fragment angular distributions, causing the most probable proton and electron emission directions to deviate substantially from the principal
z axis. These findings demonstrate that the spatial and temporal geometry of orthogonal laser fields provides an additional degree of freedom for controlling ultrafast electron-nuclear dynamics.
Orthogonally polarized two-color sequential laser pulses are used to control the electron localization in the dissociation of H
2+. The first single attosecond pulse, whose polarization axis is perpendicular to the molecular axis, excites H
2+ from $1s{\ensuremath{\sigma}}_{g}$ to $2p{\ensuremath{\pi}}_{u}$, and the time-delayed infrared pulse, whose polarization axis is parallel to the molecular axis, steers the electron between two nuclei. The simulation of the time-dependent Schr\"odinger equation predicts the control degree of the electron localization can be up to 90
with the current laser technology. In this article, we reveal that the mechanism for this asymmetric localization is due to the mixture of $2p{\ensuremath{\pi}}_{g}$ and $2p{\ensuremath{\pi}}_{u}$, instead of $1s{\ensuremath{\sigma}}_{g}$and $2p{\ensuremath{\sigma}}_{u}$ in the previous studies.
Within the Born-Oppenheimer approximation, we build a multichannel model to simulate the dissociation of
H2+ in strong laser fields. Two applications of this model are presented: first, orthogonally polarized UV and infrared pulses are used to dissociate
H2+ into $2p{\ensuremath{\pi}}_{u}$ and $3d{\ensuremath{\pi}}_{g}$ states, whose superposition results in asymmetric electron localization after the dissociation; second, two orthogonally polarized UV pulses are introduced to trigger competing Rabi oscillations among $1s{\ensuremath{\sigma}}_{g}$, $2p{\ensuremath{\sigma}}_{u}$, $3d{\ensuremath{\sigma}}_{g}$ and $2p{\ensuremath{\pi}}_{u}$ states. This study shows the dissociation of
H2+ can be steered into selected electronic states with controllable probabilities with state-of-the-art laser technologies.