Conservation laws for Electron Vortices in StrongField Ionisation
Abstract
We investigate twisted electrons with a well defined orbital angular momentum, which have been ionised via a strong laser field. By formulating a new variant of the wellknown strong field approximation, we are able to derive conservation laws for the angular momenta of twisted electrons in the cases of linear and circularly polarised fields. In the case of linear fields, we demonstrate that the orbital angular momentum of the twisted electron is determined by the magnetic quantum number of the initial bound state. The condition for the circular field can be related to the famous ATI peaks, and provides a new interpretation for this fundamental feature of photoelectron spectra. We find the length of the circular pulse to be a vital factor in this selection rule and, employing an effective frequency, we show that the photoelectron OAM emission spectra is sensitive to the parity of the number of laser cycles. This work provides the basic theoretical framework with which to understand the OAM of a photoelectron undergoing strong field ionisation.
 Publication:

arXiv eprints
 Pub Date:
 February 2021
 arXiv:
 arXiv:2102.07453
 Bibcode:
 2021arXiv210207453K
 Keywords:

 Physics  Atomic Physics;
 Physics  Optics;
 Quantum Physics
 EPrint:
 11 pages, 4 figures and 44 equations. Publication prepared for the EPJ D Topical Issue: Quantum Aspects of Attoscience