Simulation of Auger decay dynamics in the hard X-ray regime: HCl as a showcase

Abstract

Auger decay after photoexcitation or photoemission of an electron from a deep inner shell in the hard x-ray regime can be rather complex, implying multitude of phenomena such as multiple-step...

Multireference Approach to Normal and Resonant Auger Spectra Based on the One-Center Approximation

“…18 , 19 Moreover, the Auger decay around the Cl 1s threshold of HCl has been recently simulated, considering the evolution of the relaxation process, including both electron and nuclear dynamics. 20 Adding to that is the fact that AES does not obey the same dipole transition rules as XAS does, so AES/RAES can be used as a powerful tool to probe dark states and couple to nuclear dynamics. 11 − 13 However, from the computational point of view, for AES/RAES to be used effectively as a probe of (excited-state) nuclear dynamics, one should efficiently deal with one of the major complications in the computation of Auger spectra, namely the description of the electron in the continuum.…”

“…The high sensitivity of AES/RAES to electronic and nuclear dynamics encouraged experimentalists to explore it to unravel underlying electron and nuclear dynamics of photoexcited molecules. − In the case of halogen-containing molecules, the photoexcited repulsive σ* states expose the competition between nuclear dynamics and resonant Auger electron emission, because of the fact that both Auger decay and direct dissociation occur on the femtosecond time scale. − In a series of recent studies, it was also demonstrated that ultrafast dissociation, distinguished by means of its fingerprint in the RAES, is a practical mechanism of distributing the molecular internal energy of the L -edge photoexcited systems in small molecules like HCl as well as in heavier ones, such as CH 2 Cl 2 and CHCl 3 . , Moreover, the Auger decay around the Cl 1s threshold of HCl has been recently simulated, considering the evolution of the relaxation process, including both electron and nuclear dynamics . Adding to that is the fact that AES does not obey the same dipole transition rules as XAS does, so AES/RAES can be used as a powerful tool to probe dark states and couple to nuclear dynamics. − However, from the computational point of view, for AES/RAES to be used effectively as a probe of (excited-state) nuclear dynamics, one should efficiently deal with one of the major complications in the computation of Auger spectra, namely the description of the electron in the continuum.…”

“…In this regard, both OCA and population-analysis-based methods are very attractive candidates to set up computational protocols that couple the calculation of the Auger spectral signatures with nuclear dynamics. A few studies have already been presented, ranging from small molecules ,,− to larger ones, such as ethyl trifluoroacetate …”

Multi-Reference Approach to Normal and Resonant Auger Spectra Based on the One-Center Approximation

“…[17][18][19] In a series of recent studies, it was also demonstrated that ultrafast dissociation, distinguished by means of its fingerprint in the RAES, is a practical mechanism of distributing the molecular internal energy of the L-edge photoexcited systems in small molecules like the relaxation process, including both electron and nuclear dynamics. 20 Summing to that is the fact that AES does not obey the same dipole transition rules as XAS does, so AES/RAES can be used as a powerful tool to probe dark states and couple to nuclear dynamics. [11][12][13] However, from the computational point of view, for AES/RAES to be used effectively as a probe of (excited-state) nuclear dynamics, one should efficiently deal with one of the major complications in the computation of Auger spectra, namely the description of the electron in the continuum.…”

“…In this regard, both OCA and population-analysis-based methods present themselves as very attractive candidates to set up computational protocols that couple the calculation of the Auger spectral signatures with nuclear dynamics. Where a few studies have been presented so far using the one-center approximation on small systems such as diatomics 20,61 or triatomics, 44,[62][63][64] simulations aimed at complex molecules are still missing.…”