Molecular Auger Interferometry

We introduce and present a theory of interferometric measurement of a normal Auger decay lifetime in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-color ($\omega /2\omega$) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups the relative $\omega /2\omega$ phase modulates the total ionization yield. A simple analytical formula is derived for the extraction of the lifetimes of Auger-active states from a molecular Auger interferogram, circumventing the need in either high-resolution or attosecond spectroscopy. We demonstrate the principle of the interferometric Auger lifetime measurement using inner-valence decay in ${\mathrm{CH}}_3\mathrm{F}$.

Figure 1

Auger interferometry scheme for the case of the coherent control of Auger decay of a F ($2{\mathrm{s}}^{-1}$) hole in ${\mathrm{CH}}_3\mathrm{F}$ with $\omega$ and $2\omega$ laser fields. The frequency of the transition between the ground state $|0⟩={\phi }_0^{N-1}$ of the molecular cation and the AAS $|1⟩={\phi }_m^{N-1}$ (or a series of them) with energy HWHM ${\mathrm{\Gamma }}_1$ equals the fundamental frequency $\omega$. The doubly ionized final state $|E⟩={\chi }_E^n{\phi }_n^{N-2}$ can be reached by two paths: either from the ground state directly by absorbing a $2\omega$ photon or from the ground state via the intermediate AAS by absorbing two $\omega$ photons. Interference between these two transitions can be controlled by the relative phase $\varphi$ between the two laser fields.

Figure 2

The spectrum of emitted electrons ionized by a laser field (4) for the case of ${\mathrm{CH}}_3{\mathrm{F}}^{+}$ with the energy width ${\mathrm{\Gamma }}_1$ as a function of the relative phase $\varphi$. The zero of the electron energy $E$ ($y$ axis) corresponds to the resonant energy $E_0+2\omega$. The intensities of the $\omega$ field and $2\omega$ field are $6.7\times {10}^{12}\mathrm{W}/{\mathrm{cm}}^2$ and ${\mathrm{\Gamma }}_1=5\times {10}^{-3}\mathrm{a}.\mathrm{u}.$.

Figure 3

(a)–(c) Auger interferograms. The total yield of electrons emitted by a bichromatic laser field for the case of ${\mathrm{CH}}_3{\mathrm{F}}^{+}$ as a function of the relative phase $\varphi$ and the ${\mathrm{\Gamma }}_1$ ($y$ axis). (d) Modulation depth of the total yield for zero (thin solid lines) and nonzero detuning (thin dashed lines), and the resonant yield (thick dotted lines) as a function of the AAS energy width ${\mathrm{\Gamma }}_1$. The intensities are the same as for (a)–(c) used, and detunings ${\mathrm{\Delta }}_{01}$ are shown in ${10}^{-3}\mathrm{a}.\mathrm{u}.$