Atomic Physics Latest Preprints | 2019-04-23
Atomic Physics
A Coincidence Velocity Map Imaging Spectrometer for Ions and High-Energy Electrons to Study Inner-Shell Photoionization of Gas-Phase Molecules (1904.09938v1)
Utuq Ablikim, Cédric Bomme, Evgeny Savelyev, Rajesh Kushawaha, Timur Osipov, Hui Xiong, Razib Obaid, René C. Bilodeau, Nora G. Kling, Ileana Dumitriu, Sven Augustin, Shashank Pathak, Kirsten Schnorr, David Kilcoyne, Nora Berrah, Daniel Rolles
2019-04-22
We report on the design and performance of a double-sided coincidence velocity map imaging spectrometer optimized for electron-ion and ion-ion coincidence experiments studying inner-shell photoionization of gas-phase molecules with soft X-ray synchrotron radiation. The apparatus employs two microchannel plate detectors equipped with delay-line anodes for coincident, time- and position-resolved detection of photo- and Auger electrons with kinetic energies up to 300,eV on one side of the spectrometer and photoions up to 25,eV per unit charge on the opposite side. We demonstrate its capabilities by measuring valence photoelectron and ion spectra of neon and nitrogen, and by studying channel-resolved photoelectron and Auger spectra along with fragment-ion momentum correlations for chlorine
inner-shell ionization of \textit{cis}- and \textit{trans}-1,2-dichloroethene.
Adiabatic transfer of amplitude using STIRAP-like protocols generalizes to many bipartite graphs (1904.09915v1)
Koen Groenland, Carla Groenland, Reinier Kramer
2019-04-22
Adiabatic passage techniques, used to drive a system from one quantum state into another, find widespread application in physics and chemistry. We focus on the techniques called STImulated Raman Adiabatic Passage (STIRAP) and Coherent Tunnelling by Adiabatic Passage (CTAP), which employ a unique zero-energy eigenstate to transfer amplitude between ends of a linear chain. We find that many more general physical systems can use the same protocol, namely those with a (semi-)bipartite interaction graph which allows a perfect matching both when the sender is removed and when the receiver is removed. Many of the favorable stability properties of STIRAP/CTAP are inherited. We numerically test transfer between the leaves of a tree, and find surprisingly accurate transfer, especially when straddling is used. Our results open up new possibilities for coherent control and quantum state transfer in more general systems, and show that conventional STIRAP/CTAP is resilient to a large class of perturbations.
Tracking Rydberg atoms with Bose-Einstein Condensates (1810.03439v2)
Shiva Kant Tiwari, Sebastian Wüster
2018-10-08
We propose to track position and velocity of mobile Rydberg excited impurity atoms through the elastic interactions of the Rydberg electron with a host condensate. Tracks first occur in the condensate phase, but are then naturally converted to features in the condensate density or momentum distribution. The condensate thus acts analogous to the cloud or bubble chambers in the early days of elementary particle physics. The technique will be useful for exploring Rydberg-Rydberg scattering, rare inelastic processes involving the Rydberg impurities, coherence in Rydberg motion and forces exerted by the condensate on the impurities. Our simulations show that resolvable tracks can be generated within the immersed Rydberg lifetime and condensate heating is under control. Finally, we demonstrate the utility of this Rydberg tracking technique to study ionizing Rydberg collisions or angular momentum changing interactions with the condensate.
Photoelectron holographic interferometry to probe the longitudinal momentum offset at the tunnel exit (1904.09556v1)
Min Li, Hui Xie, Wei Cao, Siqiang Luo, Jia Tan, Yudi Feng, Baojie Du, Weiyu Zhang, Yang Li, Qingbin Zhang, Pengfei Lan, Yueming Zhou, Peixiang Lu
2019-04-21
Laser-induced electron tunneling underlies numerous emerging spectroscopic techniques to probe attosecond electron dynamics in atoms and molecules. The improvement of those techniques requires an accurate knowledge of the exit momentum for the tunneling wave packet. Here we demonstrate a photoelectron interferometric scheme to probe the electron momentum longitudinal to the tunnel direction at the tunnel exit by measuring the photoelectron holographic pattern in an orthogonally polarized two-color laser pulse. In this scheme, we use a perturbative 400-nm laser field to modulate the photoelectron holographic fringes generated by a strong 800-nm pulse. The fringe shift offers a direct experimental access to the intermediate canonical momentum of the rescattering electron, allowing us to reconstruct the momentum offset at the tunnel exit with high accuracy. Our result unambiguously proves the existence of nonzero initial longitudinal momentum at the tunnel exit and provides fundamental insights into the non-quasi-static nature of the strong-field tunneling.
Searching for an Exotic Spin-Dependent Interaction between Electrons at the Nanometer Scale with Molecular Rulers (1904.09428v1)
Man Jiao, Xing Rong, Hang Liang, Yi-Fu Cai, Jiangfeng Du
2019-04-20
We propose that a type of molecular rulers, which contains two electron spins with precisely adjustable distance by varying the length of the shape-persistent polymer chains, can be utilized to constrain the axial-vector mediated interaction between electron spins at the nanometer scale. With measurements of the coupling strengths between two electron spins within different molecular rulers, an improved laboratory bound of exotic dipole-dipole interaction between electrons is established within the force range from 3 to 220 nm. The upper bound of the coupling
at 200 nm is
, which is about 20 times more stringent than previous limits.
Repulsive Fermi Polarons and Their Induced Interactions in Binary Mixtures of Ultracold Atoms (1808.00040v3)
S. I. Mistakidis, G. C. Katsimiga, G. M. Koutentakis, P. Schmelcher
2018-07-29
We explore repulsive Fermi polarons in one-dimensional harmonically trapped few-body mixtures of ultracold atoms using as a case example a
Li-
K mixture. A characterization of these quasiparticle-like states, whose appearance is signalled in the impurity's radiofrequency spectrum, is achieved by extracting their lifetime and residua. Increasing the number of
Yb system. This distance is further shown to be indicative of the generation of entanglement independently of the size of the bath (
Correcting symmetry imperfections in linear multipole traps (1807.10500v2)
J. Pedregosa-Gutierrez, C. Champenois, M. Houssin, M. R. Kamsap, M. Knoop
2018-07-27
Multipole radio-frequency traps are central to collisional experiments in cryogenic environments. They also offer possibilities to generate new type of ion crystals topologies and in particular the potential to create infinite 1D/2D structures: ion rings and ion tubes. However, multipole traps have also been shown to be very sensitive to geometrical misalignment of the trap rods, leading to additional local trapping minima. The present work proposes a method to correct non-ideal potentials, by modifying the applied radio-frequency amplitudes for each trap rod. This approach is discussed for the octupole trap, leading to the restitution of the ideal Mexican-Hat-like pseudo-potential, expected in multipole traps. The goodness of the compensation method is quantified in terms of the choice of the diagnosis area, the residual trapping potential variations, the required adaptation of the applied radio-frequency voltage amplitudes, and the impact on the trapped ion structures. Experimental implementation for macroscopic multipole traps is also discussed, in order to propose a diagnostic method with respect to the resolution and stability of the trap drive. Using the proposed compensation technique, we discuss the feasibility of generating a homogeneous ion ring crystal, which is a measure of quality for the obtained potential well.
Multi-Channel Interference in Resonance-Like Enhancement of High-Order Above-Threshold Ionization (1812.05283v2)
Long Xu, Libin Fu
2018-12-13
The intensity-dependent resonance-like enhancement phenomenon in high-order above-threshold ionization spectrum is a typical quantum effect for atoms or molecules in the intense laser field, which has not been well understood. The calculations of TDSE are in remarkable agreement with the experimental data, but they can not clarify the contributions of the bound states. The semi-classical approach of strong field approximation, in which no excited states are involved, can obtain the similar phenomenon, but the laser intensities of enhanced regions predicted by SFA are inconsistent with the results of TDSE. In this letter, a new fully quantum model is established from TDSE with not any excited states. Two types of enhanced structures, unimodal and multimodal structures, are found in the results of TDSE and model. Besides, the calculations of model reproduce the key features of the results of TDSE. It shows that the excited states are not the key factor in the resonance-like enhancements in our calculated system, since there are not any excited states in our model. Based on the calculations of our model, we show that such resonance-like enhancements are caused by the constructive interference of different momentum transfer channels. Last, the Fano-like lineshapes are also discussed for the features of multi-channel interference.
Dynamical enhancement of nonparaxial effects in the electromagnetic field of a vortex electron (1902.08787v2)
Dmitry Karlovets
2019-02-23
A quantum state of an electron influences its electromagnetic field. If a spatial profile of the electron wave packet is not Gaussian, the particle may acquire additional intrinsic multipole moments, which alter its field, especially at small distances. Here the fields of a vortex electron with orbital angular momentum
are obtained in a form of a multipole expansion with an electric quadrupole term kept by using the generalized (non-paraxial) Laguerre-Gaussian beams. The quadrupole contribution arises beyond a paraxial approximation, is linearly enhanced for highly twisted packets with
, and can be important for the interactions of twisted beams with bulk matter and artificial structures. Moreover, this term results in an azimuthal asymmetry of the magnetic field in a rest frame of the electron, which appears thanks to the spreading of the packet with time. Thus, somewhat contrary to physical intuition, the spreading may enhance non-paraxial phenomena. For the available electron beams, this asymmetry can in principle be reliably detected, which would be experimental evidence of a non-paraxial effect with the vortex electrons.
Gravity surveys using a mobile atom interferometer (1904.09084v1)
Xuejian Wu, Zachary Pagel, Bola S. Malek, Timothy H. Nguyen, Fei Zi, Daniel S. Scheirer, Holger Müller
2019-04-19
Mobile gravimetry is important in metrology, navigation, geodesy, and geophysics. Atomic gravimeters could be among the most accurate mobile gravimeters, but are currently constrained by being complex and fragile. Here, we demonstrate a mobile atomic gravimeter, measuring tidal gravity variations in the laboratory as well as surveying gravity in the field. The tidal gravity measurements achieve a sensitivity of 37
Gal/
and a long-term stability of better than 2
