FARIA1	Quantum interference of different channels in nonsequential double ionization
Type	Theoretical
#students	2
Orientation	Why is the scientific problem of interest at all?
How	How is the research going to shed light on the given problem?. In previous work, we have performed a series of studies of the RESI mechanism using semi-analytical methods. In particular, we have shown that the electron momentum distributions equally occupy the four quadrants of the plane spanned by the momentum components parallel to the laser-field polarization, and that their shapes are strongly influenced by the atomic state, or molecular orbital to which the second electron has been excited [1,2]. These findings, however, do not explain recent experiments in which the NSDI correlated probability density was found to occupy only the second and fourth quadrants of the parallel-momentum plane [3]. In a recent theoretical paper, it has been proposed that these features are caused by the quantum interference between several ionization and excitation channels [4].
What	What is the specific thing that the student will do, and how does it fit inside the overall project? We will assess the influence of different channels and coherent superpositions of states in RESI electron-momentum distributions. The aims of the project are twofold: (a) to assess which channels lead to the experimental findings and whether our results agree with those in [4]; (b) employing the information obtained in (a), control the shapes of the electron-momentum distributions by an appropriate choice of driving-pulse parameters, such as its shape, frequency and polarization, and initial coherent superpositions of states. One student should focus on atomic systems, while the other student should concentrate on molecules. In the latter case, an assessment of the interference caused by electron emission in spatially separated centres must be made. The student(s) will employ the strong-field approximation, and the steepest descent method
Special Knowlegde	Mathematica and/or C++
Supervisor	Dr Carla Faria c.faria@ucl.ac.uk
References (optional)	http://www.homepages.ucl.ac.uk/~ucapcfi/ [1] T. Shaaran, M.T. Nygren and C. Figueira de Morisson Faria, Phys. Rev. A 81, 063413 (2010). [2] T. Shaaran, B.B. Augstein and C. Figueira de Morisson Faria, Phys. Rev. A 84, 013429 (2011). [3] Y. Q. Liu et al, Phys. Rev. Lett. 101, 053001 (2008). [4] X. Hao et al, Phys. Rev. Lett. 112, 073002 (2014).