4 2.0 4.0 6.0 8.0 10.0 12.0 KER (eV) 0 100 200 300 400 500 Yield (arb. units) 4.0 (EXP.) 4.0 (SIM.) 3.5 (SIM.) 3.0 (SIM.) 4 6 8 10 12 KER (eV) 0 0.0005 0.001 0.0015 Yield (arb. units) 4.8 6.4 8.1 9.4 11.0 12.5 15.0 FIG. 2: Comparison of the experimental and simulation KER spectra. The red dotted line is related to the experimental results [3] for a 480 nm laser pulse with peak intensity I=4 . 0 × 10 14 W cm − 2 and $_{∼}$100 ± 10 fs pulse duration. The black solid, grey solid, and blue dot-dash lines show simulation results for 480 nm, τ$_{p}$ ≃ 40 fs laser pulses with peak intensities 4 . 0 × 10 $^{14}$, 3 . 5 × 10 14 ,and 3 . 0 × 10 14 W cm − 2 respectively. FIG. 3: Time-dependent construction of the KER Spectrum that is related to the peak intensity 4 . 0 × 10 14 W cm − 2 shown in Fig. 2. The high-energy band of the KER Spectrum appears at first between $_{∼}$4.8 to $_{∼}$8 cycles of the laser pulse. After this time, the low-energy band of the KER Spectrum appears. been used to derive the R-dependent ionization rate of D + 2 in most previous studies [20–22]. In this figure, we also show the internuclear populations for the different time intervals shown in Fig. 3. This figure shows explic- itly that the high-energy band of the KER spectrum in Fig. 3, that is constructed between ∼ 4 . 8 − 8 cycles, has a strong ionization rate about ∼ 4 − 5 internuclear dis- tances and the low-energy band of the KER spectrum (Fig. 3), that is constructed between ∼ 8 . 1 − 12 . 5 cycles, has a relatively strong ionization rate about ∼ 6 − 7 inter- nuclear distances. After 12.5 cycles, the intensity of the laser field becomes considerably low (Fig. 1) and a signif- icant population of D + 2 was becomes ionized as shown in Fig. 5. Therefore it is impossible to appear an enhanced ionization signal for larger internuclear distances. In Coulomb explosion imaging [23], we want to re-