Fig. 1. Schematic diagram of the coordinate system formed by the collision of an ion or proton with a molecule.

Fig. 2. Time evolution of the molecular orientation (a) in the absence of an external field and (b) being steered by laser pulses. Green line, THz laser pulse; orange line, two-color laser pulse; blue line, combination of two laser pulses. b = 10 a.u., v = 0.06 a.u., E₀₁ = 5.1×10⁷ V/cm, E₀₂ = 1.0 × 10⁷ V/cm, τ = 450 ps, ω₁ = 12,500 cm⁻¹, t_d = 2.16 ps, ω_THz = 36 cm⁻¹, φ = π, and T = 0 K in all.

Fig. 3. Maximal degree of orientation as a function of the (a) collision velocity and (b) impact parameter.

Fig. 4. Maximal degree of orientation 〈cos θ〉_max as a function of the field intensity of the (a) two-color and (b) THz field, where the b = 5 a.u., v = 0.03 a.u., and T = 0 K.

Fig. 5. Maximal degree of the orientation 〈cos θ〉_max as a function of the (a) CEP and (b) frequency of the THz laser pulse, where b = 5 a.u., v = 0.03 a.u., E₀₁ = 5.2 × 10⁷ V/cm, E₀₂₁ = 0.45 × 10⁷ V/cm, and T = 0 K.

Fig. 6. (a) Time evolution curves of  orientation degree and (b) the rotational population of different rotational states at the temperature T = 0 K (blue line), 5 K (orange line), and 10 K (green line), while b = 5 a.u., v = 0.03 a.u., E₀₁ = 5.2 × 10⁷ V/cm, E₀₂ = 0.45 × 10⁷ V/cm, φ = 1.2π, and ω_THz = 26 cm^-1.