Vibrational effect in conventional and laser-induced electron diffractions

Comprehensively and accurately characterizing matter information is the ultimate goal of physics and chemistry, which can be achieved by conventional electron diffraction (CED) and, recently, laser-induced electron diffraction (LIED). Remarkably, the latter method allows the retrieval of molecular structures during its rapid dynamical processes; however, the nuclear vibrational effect is still understudied. Moreover, if the vibrational effect in CED and LIED is substantial, a natural question is whether it is possible to reconstruct anharmonic interatomic potential from their measurements. The goal of this paper is to study the vibrational effect in LIED images, and then to examine the possibility of retrieving anharmonic interatomic potential from CED and LIED. To achieve this goal, we simulate the diffraction images incorporating the nuclear vibrations induced either by thermal vibration in CED or by an intense laser interaction in LIED. We show that the vibrational effect in LIED is significantly enhanced compared to that in the CED due to the presence of intense laser interaction. As a consequence, the diffraction images in LIED are much more sensitive to the potential shape; thus, it is possible to retrieve anharmonic interatomic potential. We also indicate that in CED, this extraction is also possible but requires far more stringent measurements. Although the retrieval is performed for simple Morse potential in this study, it can be generalized to retrieve other parameterized anharmonic interatomic potentials. In our study, the LIED images are simulated numerically but can be experimentally measured as well.