Rakesh Choubisa
Since the experimental realization of electron vortex (twisted) beams in 2010 [1-2], there has been extensive work on the vortex electrons, particularly in the field of its interaction with matter. Due to additional degrees of freedom with the electron vortex beam, its interaction with the matter is expected to be different from that for the conventional beam (plane wave beam). Because of this, the vortex particles may be a better tool for probing their interactions with the matter. For example, Bliokh et al. [3] have discussed the applications of vortex beams in electron microscopy for the mapping of magnetic and chiral properties at atomic-resolution as well as other phenomena involving vortex electrons outside of the TEM context to elucidate the importance of the vortex beam.
During the last five years, our group has done numerous studies on the vortex electron collision with the atomic and molecular targets [4-8]. We investigated the angular distribution of the triple differential cross sections (TDCS) and five-fold differential cross sections (5DCS) for (e,2e) and (e,3e) processes with the twisted electron beam. We developed our formalism in the first Born approximation in which we describe the incident twisted electron as Bessel wave function, scattered electron as the plane wave, and ejected electron as the Coulomb wave function for the (e, 2e) and 2 Coulomb wave with Gamow factor (2CG) for the (e, 3e) processes. We use different types of wave functions for the initial state of the target. In addition to this, we also studied (e,2e) processes on atomic and molecular targets with the twisted electron beam in the presence of an external laser field. Recently, we have extended our studies for the elastic scattering of twisted electrons with the polyatomic molecular targets using all electrons approach.
Through these studies, we discussed the effects of the Orbital Angular Momentum (OAM or TAM), opening angle and the impact parameter of the twisted electron beam on the cross sections (differential and total) of these processes and also compared these calculations with that of the plane wave. We will discuss these aspects in the workshop as well as the future prospects of our studies especially from the perspective of the photon vortex beam.
References:
[1] Uchida, M., Tonomura, A. Generation of electron beams carrying orbital angular momentum. Nature 464, 737–739 (2010). https://doi.org/10.1038/nature08904[2] Verbeeck, J., Tian, H. & Schattschneider, P. Production and application of electron vortex beams. Nature 467, 301–304 (2010). https://doi.org/10.1038/nature09366
[3] Bliokh, K.Y. et. al. , Theory and applications of free-electron vortex states, Physics Reports, 690, Pages 1-70 (2017)
https://doi.org/10.1016/j.physrep.2017.05.006.
[4] Dhankhar, N., Mandal, A., & Choubisa, R. Double ionization of helium by twisted electron beam. Journal of Physics B: Atomic, Molecular and Optical Physics, 53(15), 155203 (2020).https://doi.org/10.1088/1361-6455/ab8718
[5] Mandal, A., Dhankhar, N., Sébilleau, D., & Choubisa, R. (2021). Semirelativistic (e, 2 e) study with a twisted electron beam on Cu and Ag. Physical Review A, 104(5), 052818. https://doi.org/10.1103/PhysRevA.104.052818
[6] Dhankhar, N., & Choubisa, R. (2022). Triple-differential cross section for the twisted-electron-impact ionization of the water molecule. Physical Review A, 105(6), 062801.https://doi.org/10.1103/PhysRevA.105.062801
[7] Dhankhar, N., Pinto, R. S., & Choubisa, R. (2024). Laser-assisted (e, 2e) study with twisted electron beam on H-atom. Journal of Physics B: Atomic, Molecular and Optical Physics, 57(9), 095202.https://dx.doi.org/10.1088/1361-6455/ad38f0
[8] Pinto, R. S., & Choubisa, R. (2024). Twisted electron impact elastic cross sections of polyatomic molecules: All active electron multicentered approach. ArXiv. https://arxiv.org/abs/2407.19801