Rescattering of Ultralow-Energy Electrons for Single Ionization of Ne in the Tunneling Regime

Electron emission for single ionization of Ne by 25 fs, $1.0\mathrm{P}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$ laser pulses at 800 nm has been investigated in a kinematically complete experiment using a “reaction microscope.” Mapping the complete final state momentum space with high resolution, a distinct local minimum is observed at $P_{e\parallel }=0$, where $P_{e\parallel }$ is the electron momentum parallel to the laser polarization. Whereas tunneling theory predicts a maximum at zero momentum, our findings are in good agreement with recent semiclassical predictions which were interpreted to be due to “recollision.”

Figure 1

Longitudinal and transverse momentum distribution of ${\mathrm{N}\mathrm{e}}^{1+}$ recoil ions (a) and of electrons (b) for single ionization by $1.0\mathrm{P}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$, 25 fs laser pulses at 800 nm. The $z$ scale is linear with the box sizes proportional to the number of events at a given momentum.

Figure 2

Longitudinal momentum distribution of the emitted electron ($P_{e\parallel }$) for the same conditions as in Fig. 1. Thin line: Prediction of tunneling theory [28] for $0.7\mathrm{P}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$. Thick line: Prediction of semiclassical calculation for $0.7\mathrm{P}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$ single ionization of helium [29].

Figure 3

Electron energy distribution (integrated over all emission angles) for the same conditions as in Figs. 1, 2.