Experimental evidence for selection rules in multiphoton double ionization of helium and neon

Abstract

We report on the observation of a multi peak structure in the correlated two electron energy distribution from strong field double ionization of helium using laser pulses with a wavelength of 394 nm and an intensity of 3 · 10 14 W/cm 2 . For selected regions of electron emission angles the peaks emerging at energies corresponding to an odd number of absorbed photons are suppressed. We interpret this as direct results of quantum mechanical selection rules. For Neon these features occur for even photon number. By that we attribute this effect to the parity of the continuum wave function. A comparison with analogous data for single photon double ionization is given.

Multiphoton double ionization of helium at 394 nm: A fully differential experiment

“…9). We note that in [1] we have shown data from the lowest intensity reported here. In [1] the intensity was indicated to be 3 × 10 14 .…”

“…It is the goal of the present paper to show the first fully differential experiment for multi-photon strong field double ionization. One special aspect, the quantum mechanical selection rules, has been presented in a preceding report [1]. In the multi-photon context fully differential rates entail that the number of photons and the momentum vectors of two of the three particles (ion and two electrons) in the final states are measured.…”

“…They strongly change with the energy sharing between the electrons. The aspect of selection rules in double ionization which are also visible in the presented dataset has been subject to a preceding publication [1].…”

Polarization tagging of two-photon double ionization by elliptically polarized XUV pulses

“…Polarization tagging allows to distinguish between electron emission by the first or second of the two pulses. We explore possible experimental signatures accessible with a reaction microscope [36] as recently demonstrated for ionization in the strong-field multi-photon double ionization regime [37,38].…”

Theory of Subcycle Linear Momentum Transfer in Strong-Field Tunneling Ionization

“…Because of the photon dispersion relation p ¼ E=c (c: the speed of light) included in the nondipole and relativistic regime [19][20][21], the momentum of a single photon in the propagation direction imparted on the target, p z , is very small and is usually overshadowed by the transverse momentum p ⊥ ∼ ffiffiffiffiffi ffi 2E p gained by the electron from the photon energy E, while other photon properties such as angular momentum [22][23][24] or helicity [25][26][27] have much more easily observable effects. With recent advances in detecting technologies, the small momentum shift p z in the laser propagation direction has become observable.…”