Electron spin polarization in strong-field ionization of xenon atoms

Abstract

As a fundamental property of the electron, the spin plays a decisive role in the electronic structure of matter from solids to molecules and atoms, e.g. causing magnetism. Yet, despite its importance, the spin dynamics of electrons released during the interaction of atoms with strong ultrashort laser pulses has remained unexplored. Here we report on the experimental detection of electron spin polarization by strong-field ionization of Xenon atoms and support our results by theoretical analysis. We found up to 30% spin polarization changing its sign with electron energy. This work opens the new dimension of spin to strong-field physics. It paves the way to production of subfemtosecond spin polarized electron pulses with applications ranging from probing magnetic properties of matter at ultrafast time scales to testing chiral molecular systems with subfemtosecond temporal and sub-Ångström spatial resolution. Main TextShort laser pulses provide an electric field which can be strong enough to suppress the binding potential of an atom or molecule and lead to field ionization. Electrons passing over the barrier, or tunneling just under it and emerging from the atom are subsequently driven by the laser field. So far, nearly all works exploring the electronic behavior after ionization have solely used the binding energy of the electron and the shape of the barrier as defining properties, omitting the other fundamental property of the electron -its spin. This is even more surprising as a few pioneering theoretical works have indicated the importance of the spin of the outgoing electron in strong field ionization 1,2 . From the fundamental quantum standpoint, the spin of the liberated electron should not be ignored since, first, there is correlation between this electron and the ion left behind, and, second, ionization is known to trigger spin-orbit dynamics in the ion 3 . Rare gas atoms with their

Strong Field Theories beyond Dipole Approximations in Nonrelativistic Regimes

“…The probability of spin flip is proportional to Iω 2 with I being the intensity. For parameters used in this paper and recent published experimental results [31], the probability of spin flip is significantly smaller than that of spin preservation. One may clearly see from Table II In conclusion, the standard nondipole SFA theory with or without rescattering is built based on the exact nondipole Volkov wave function in nonrelativistic regimes.…”

“…Though the velocity gauge is more intuitive to describe results, the length gauge is more quantitatively accurate in this research. Actually, the SFA in the velocity gauge gives identical photoelectron momentum distributions when the initial state has opposite magnetic quantum numbers and the laser pulse is circularly polarized, which contradicts to the known facts [30,31]. Thus all subsequent numerical calculations are carried out in length gauge in this paper.…”

Spin Polarization of Rb and Cs np P23<

“…Spin polarization of atoms with circularly-polarized optical fields [1] has proven to be a powerful tool for magnetometry [2,3], optical field-matter interactions [4], astrophysics [5], and generating hyperpolarized nuclei by spin exchange [6,7]. Several decades following the initial experiments of Hanle [8] in which the depolarization of Hg 253.7 nm resonance radiation was observed, spin polarization of Na in a rare gas background was studied [9] and the production of polarized 3 He nuclei from optically-pumped Rb atoms was reported [6].…”

Attosecond control of spin polarization in electron-ion recollision driven by intense tailored fields

“…However, despite its importance, spin polarization with strong laser fields has received no attention until very recently [12][13][14][15]. The first theoretical predictions of spin polarization in noble gases upon strong field ionization with circularly polarized light [12] have just been experimentally confirmed [14].…”

“…The possibility of inducing recollision of spin-polarized electrons with the parent ion can open new directions in attosecond spectroscopy [13,14].…”