Quantum control of ultrafast magnetic field in ${\mathrm{H}}_3^{2+}$ molecules by tricircular polarized laser pulses

We present a scheme to control the generated ultrafast magnetic field in ${\mathrm{H}}_3^{2+}$ molecules using multi-frequency tricircular pulses composed of co- and counter-rotating bicircular pulses. Simulations show that the field amplitude and the wavelength are two significant factors for magnetic field generation by tricircular pulses. Specifically, the strength of the magnetic field is linearly related to the field amplitude at λ₀ = 50 nm, while at λ₀ = 70 nm, the strength first increases and then decreases with the amplitude, this can be attributed to the resonance between the ground and excited states. Moreover, the phase and helicity of bicircular pulses are shown to have important effects on the magnetic field. The dependence of the magnetic field on the phase arises from the interference effect between multiple ionization pathways. These findings illustrate a guiding principle for controlling the magnetic field in molecular systems for future research in ultrafast magneto-optics.