Spin dynamics in HeH²⁺ molecular ion in intense laser fields

Area of Science:

• Theoretical Chemistry
• Quantum Dynamics
• Atomic and Molecular Physics

Background:

• Electron spin dynamics are crucial in molecular systems.
• Non-dipole interactions and spin-orbit coupling play significant roles in relativistic effects.
• Understanding these dynamics is key for controlling molecular behavior in intense fields.

Purpose of the Study:

• To investigate the impact of non-dipole interactions on electron spin dynamics.
• To analyze the influence of laser pulse phase and molecular alignment on relativistic characteristics.
• To explore spin-orbit coupling effects in the asymmetric HeH²⁺ molecule.

Main Methods:

• Theoretical study employing the Foldy-Wouthuysen transformation.
• Numerical solution of the Dirac equation without the Born-Oppenheimer approximation (BOA).
• Investigation of pure spin and spin-orbit current densities, spin-orbit force, and spin torque.

Main Results:

• Population oscillates between spin states, dependent on molecular orientation and laser pulse phase.
• A small spin state polarization occurs even without spin-orbit coupling.
• Spin and spin-orbit current densities exhibit phase-dependence and differential responses to the laser pulse phase.

Conclusions:

• Non-dipole interactions significantly affect electron spin dynamics in HeH²⁺.
• Laser pulse phase and molecular alignment are critical parameters for controlling spin dynamics.
• Relativistic effects, including spin polarization, are observable and controllable in this system.