Observation and Control of Laser-Enabled Auger Decay

Single-photon laser-enabled Auger decay (spLEAD) is predicted theoretically [B. Cooper and V. Averbukh, Phys. Rev. Lett. 111, 083004 (2013)] and here we report its first experimental observation in neon. Using coherent, bichromatic free-electron laser pulses, we detect the process and coherently control the angular distribution of the emitted electrons by varying the phase difference between the two laser fields. Since spLEAD is highly sensitive to electron correlation, this is a promising method for probing both correlation and ultrafast hole migration in more complex systems.

Figure 1

Schematic diagram for the ionization of Ne $2s{}^{2}2p^5$. Center: initial state. Left (blue arrows): (1) the spLEAD process follows (2) absorption of one $\omega$ photon. Right (red arrows): direct ionization by $2\omega$, process (3).

Figure 2

Electron kinetic energy spectra of atomic Ne irradiated by $\omega =26.91\mathrm{eV}$ and $2\omega =53.82\mathrm{eV}$ (dashed blue curve) and $2\omega$ only (continuous red curve).

Figure 3

Asymmetry $A(\eta )$ of photoelectron angular distributions corresponding to the final ionic states ${}^{1}S$, ${}^{1}D$, and ${}^{3}P$ of ${\mathrm{Ne}}^{2+}$, as a function of the phase shift between the first and second harmonic. The asymmetry $A(\eta )$ is defined as the difference between the emission in one hemisphere ($0<\theta <\pi /2$) and the other ($\pi /2<\theta <\pi$), divided by the sum of the emission.