Correlation-driven charge migration as an initial step of the dynamics in correlation bands

We present quantum dynamics calculations showing that the electron-correlation-driven charge migration occurring in the correlation band of ionized molecules can lead to a redistribution of the charge which increases the stability of the system. These calculations offer an interpretation of recent experimental results obtained for adenine for which the stabilization induced by the electron-correlation-driven charge migration leads to a modification of the fragmentation pattern of the molecule after subsequent ionization. We argue that this charge-migration-induced stabilization is a general mechanism and discuss its implications for the development of attochemistry and how it can be understood in the context of the ultrafast, nonadiabatic relaxation taking place in highly excited molecular cations.

Figure 1

(a) Ionization spectrum of adenine computed with ADC(3). The dashed orange line, located at 23.5 eV, shows the position of the lowest double-ionization potential (DIP) as reported in Ref. [39]. (b) Zoom of the correlation-band region. The contributions of the one-hole configurations corresponding to the removal of an electron from $\mathrm{HOMO}-15, \mathrm{HOMO}-16, \mathrm{HOMO}-17$, and $\mathrm{HOMO}-18$ are depicted with cyan, red, green, and yellow, respectively.

Figure 2

Evolution of the hole occupations following the removal of an electron from $\mathrm{HOMO}-16$. A negative hole occupation means that an electron is promoted to a virtual orbital. We see that for time less than 3 fs, the initial hole (red dashed curve) migrates preferentially to $\pi$ orbitals (depicted in black).

Figure 3

Snapshot of the hole density at 0, 1, 2, and 3 fs following the removal of an electron from $\mathrm{HOMO}-16$. Lack of electron density (hole) is depicted in green, while areas with excess electron density are depicted in orange.