Figure 2 . The Tσ(s ) of the CW (θ = 0.0°, -60.0°, -120.0°, -180.0°) and CCW (θ = 0.0°, 60.0°, 120.0°, 180.0°) of the torsional C1-N7 BCP bond-path for the E -fields = -20×10-4 au, -100×10-4 au and -200×10-4 au are presented in the left panels respectively, the corresponding E -fields = +20×10-4 au, +100×10-4 au and +200×10-4 au are presented in the right panels of sub-figure (a-c) respectively.