Intertwined electron-nuclear motion in frustrated double ionization in driven heteronuclear molecules

We study frustrated double ionization in a strongly-driven heteronuclear molecule HeH$^{+}$ and compare with H$_2$. We compute the probability distribution of the sum of the final kinetic energies of the nuclei for strongly-driven HeH$^{+}$. We find that this distribution has more than one peak for strongly-driven HeH$^{+}$, a feature we do not find to be present for strongly-driven H$_{2}$. Moreover, we compute the probability distribution of the n quantum number of frustrated double ionization. We find that this distribution has several peaks for strongly-driven HeH$^{+}$, while the respective distribution has one main peak and a "shoulder" at lower n quantum numbers for strongly-driven H$_{2}$. Surprisingly, we find this feature to be a clear signature of the intertwined electron-nuclear motion

t-SURFF: Fully Differential Two-Electron Photo-Emission Spectra

The time dependent surface flux (t-SURFF) method is extended to single and double ionization of two electron systems. Fully differential double emission spectra by strong pulses at extreme UV and infrared wave length are calculated using simulation volumes that only accommodate the effective range of the atomic binding potential and the quiver radius of free electrons in the external field. For a model system we find pronounced dependence of shake-up and non-sequential double ionization on phase and duration of the laser pulse. Extension to fully three-dimensional calculations is discussed

Photo-electron momentum spectra from minimal volumes: the time-dependent surface flux method

The time-dependent surface flux (t-SURFF) method is introduced for computing of strong-field infrared photo-ionization spectra of atoms by numerically solving the time-dependent Schr\"odinger equation on minimal simulation volumes. The volumes only need to accommodate the electron quiver motion and the relevant range of the atomic binding potential. Spectra are computed from the electron flux through a surface, beyond which the outgoing flux is absorbed by infinite range exterior complex scaling (irECS). Highly accurate infrared photo-electron spectra are calculated in single active electron approximation and compared to literature results. Detailed numerical evidence for performance and accuracy is given. Extensions to multi-electron systems and double ionization are discussed.Comment: 18 pages, 5 figure

Two--Electron Atoms in Short Intense Laser Pulses

We discuss a method of solving the time dependent Schrodinger equation for atoms with two active electrons in a strong laser field, which we used in a previous paper [A. Scrinzi and B. Piraux, Phys. Rev. A 56, R13 (1997)] to calculate ionization, double excitation and harmonic generation in Helium by short laser pulses. The method employs complex scaling and an expansion in an explicitly correlated basis. Convergence of the calculations is documented and error estimates are provided. The results for Helium at peak intensities up to 10^15 W/cm^2 and wave length 248 nm are accurate to at least 10 %. Similarly accurate calculations are presented for electron detachment and double excitation of the negative hydrogen ion.Comment: 14 pages, including figure

Spectrum of Neutral Helium in Strong Magnetic Fields

We present extensive and accurate calculations for the excited state spectrum of spin-polarized neutral helium in a range of magnetic field strengths up to $10^{12}$ G. Of considerable interest to models of magnetic white dwarf stellar atmospheres, we also present results for the dipole strengths of the low lying transitions among these states. Our methods rely on a systematically saturated basis set approach to solving the Hartree--Fock self-consistent field equations, combined with an ``exact'' stochastic method to estimate the residual basis set truncation error and electron correlation effects. We also discuss the applicability of the adiabatic approximation to strongly magnetized multi-electron atoms.Comment: 19 pages, 7 figures, 10 table

“'Subaltern Victims’ or ‘Useful Resources”? Migrant Women in the Lega Nord Ideology and Politics"

Since the mid-2000s we have witnessed the emergence of a new phenomenon in several European countries: the mobilisation of issues of women’s rights and gender equality by populist radical right parties (PRR)1 in anti-immigration campaigns. Recent contributions have illustrated some aspects and contradictions of these phenomena, for instance in relation to the PRR parties’ embrace not only of women’s but also gay rights (Bracke 2011). Others have described the double standard applied to migrant men and women in the context of raising hostility towards the Muslim population, not only by PRR parties, but within the mainstream more generally; whereas Muslim men have been mostly described as representing a social and cultural danger to European societies as well as being inherently misogynist, Muslim women have been portrayed prevalently as victims to be rescued (Abu-Lughod 2013). Little however has been written on the gendered ideology and strategies of these parties, particularly when it comes to addressing the issue of migrant women. This chapter aims to address these gaps in the scholarly literature by focusing on the gendered dimensions of anti-immigration ideology, policy and politics in the case of the LN. In particular, we draw on the empirical findings of two research projects to analyse the instrumental mobilisation of women’s rights by the LN to stigmatise migrant, particularly Muslim, communities

Atom interferometry with trapped Bose-Einstein condensates: Impact of atom-atom interactions

Interferometry with ultracold atoms promises the possibility of ultraprecise and ultrasensitive measurements in many fields of physics, and is the basis of our most precise atomic clocks. Key to a high sensitivity is the possibility to achieve long measurement times and precise readout. Ultra cold atoms can be precisely manipulated at the quantum level, held for very long times in traps, and would therefore be an ideal setting for interferometry. In this paper we discuss how the non-linearities from atom-atom interactions on one hand allow to efficiently produce squeezed states for enhanced readout, but on the other hand result in phase diffusion which limits the phase accumulation time. We find that low dimensional geometries are favorable, with two-dimensional (2D) settings giving the smallest contribution of phase diffusion caused by atom-atom interactions. Even for time sequences generated by optimal control the achievable minimal detectable interaction energy $\Delta E^{\rm min}$ is on the order of 0.001 times the chemical potential of the BEC in the trap. From there we have to conclude that for more precise measurements with atom interferometers more sophisticated strategies, or turning off the interaction induced dephasing during the phase accumulation stage, will be necessary.Comment: 28 pages, 13 figures, extended and correcte

Interpreting Attoclock Measurements of Tunnelling Times

Resolving in time the dynamics of light absorption by atoms and molecules, and the electronic rearrangement this induces, is among the most challenging goals of attosecond spectroscopy. The attoclock is an elegant approach to this problem, which encodes ionization times in the strong-field regime. However, the accurate reconstruction of these times from experimental data presents a formidable theoretical challenge. Here, we solve this problem by combining analytical theory with ab-initio numerical simulations. We apply our theory to numerical attoclock experiments on the hydrogen atom to extract ionization time delays and analyse their nature. Strong field ionization is often viewed as optical tunnelling through the barrier created by the field and the core potential. We show that, in the hydrogen atom, optical tunnelling is instantaneous. By calibrating the attoclock using the hydrogen atom, our method opens the way to identify possible delays associated with multielectron dynamics during strong-field ionization.Comment: 33 pages, 10 figures, 3 appendixe