Search results for "fluid"
showing 10 items of 5513 documents
Precision atomic physics techniques for nuclear physics with radioactive beams
2012
Atomic physics techniques for the determination of ground-state properties of radioactive isotopes are very sensitive and provide accurate masses, binding energies, Q-values, charge radii, spins, and electromagnetic moments. Many fields in nuclear physics benefit from these highly accurate numbers. They give insight into details of the nuclear structure for a better understanding of the underlying effective interactions, provide important input for studies of fundamental symmetries in physics, and help to understand the nucleosynthesis processes that are responsible for the observed chemical abundances in the Universe. Penning-trap and and storage-ring mass spectrometry as well as laser spe…
Quantum localization and bound state formation in Bose-Einstein condensates
2010
We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity and a bou…
Narrow-band pulsed electron source based on near-threshold photoionization of Cs in a magneto-optical trap
2019
The newly developed method of time-of-flight (ToF) momentum microscopy was used to analyse the cold electron emission from a Cs 3D magneto-optical trap (MOT). Three-step resonant photoionization was implemented via two intermediate states (6P3/2 pumped with 852 nm laser and 7S1/2 with 1470 nm) and a tuneable femtosecond Ti:sapphire laser for the final ionization step. The magnetic field of the MOT is switched off during the photoionization step. The natural bandwidth of the fs-laser is reduced to 4 meV using optical spectral filters. Precise tuning of the photon energy makes it possible to observe the transition regime between direct photoemission into the open continuum and field induced i…
Measurement of untruncated nuclear spin interactions via zero- to ultralow-field nuclear magnetic resonance
2015
Zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultra-low-field NMR measurements of residual dipolar couplings in acetonitrile…
Sawtooth-wave adiabatic-passage slowing of dysprosium
2018
We report on sawtooth wave adiabatic passage (SWAP) slowing of bosonic and fermionic dysprosium isotopes by using a 136 kHz wide transition at 626 nm. A beam of precooled atoms is further decelerated in one dimension by the SWAP force and the amount of atoms at near zero velocity is measured. We demonstrate that the SWAP slowing can be twice as fast as in a conventional optical molasses operated on the same transition. In addition, we investigate the parameter range for which the SWAP force is efficiently usable in our set-up, and relate the results to the adiabaticity condition. Furthermore, we add losses to the hyperfine ground-state population of fermionic dysprosium during deceleration …
Observation of a narrow inner-shell orbital transition in atomic erbium at 1299 nm
2021
We report on the observation and coherent excitation of atoms on the narrow inner-shell orbital transition, connecting the erbium ground state $[\mathrm{Xe}] 4f^{12} (^3\text{H}_6)6s^{2}$ to the excited state $[\mathrm{Xe}] 4f^{11}(^4\text{I}_{15/2})^05d (^5\text{D}_{3/2}) 6s^{2} (15/2,3/2)^0_7$. This transition corresponds to a wavelength of 1299 nm and is optically closed. We perform high-resolution spectroscopy to extract the $g_J$-factor of the $1299$-nm state and to determine the frequency shift for four bosonic isotopes. We further demonstrate coherent control of the atomic state and extract a lifetime of 178(19) ms which corresponds to a linewidth of 0.9(1) Hz. The experimental findi…
Anisotropic light-shift and magic-polarization of the intercombination line of Dysprosium atoms in a far-detuned dipole trap
2018
We characterize the anisotropic differential ac-Stark shift for the Dy $626$ nm intercombination transition, induced in a far-detuned $1070$ nm optical dipole trap, and observe the existence of a "magic polarization" for which the polarizabilities of the ground and excited states are equal. From our measurements we extract both the scalar and tensorial components of the dynamic dipole polarizability for the excited state, $\alpha_E^\text{s} = 188 (12)\,\alpha_\text{0}$ and $\alpha_E^\text{t} = 34 (12)\,\alpha_\text{0}$, respectively, where $\alpha_\text{0}$ is the atomic unit for the electric polarizability. We also provide a theoretical model allowing us to predict the excited state polari…
Coherence and entanglement dynamics of vibrating qubits
2017
We investigate the dynamics of coherence and entanglement of vibrating qubits. Firstly, we consider a single trapped ion qubit inside a perfect cavity and successively we use it to construct a bipartite system made of two of such subsystems, taken identical and noninteracting. As a general result, we find that qubit vibration can lead to prolonging initial coherence in both single-qubit and two-qubit system. However, despite of this coherence preservation, we show that the decay of the entanglement between the two qubits is sped up by the vibrational motion of the qubits. Furthermore, we highlight how the dynamics of photon-phonon correlations between cavity mode and vibrational mode, which…
Ca impurity in small mixed He-4-He-3 clusters
2009
The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the He-4-He-3 interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for He-4 clusters, and to become fully solvated for He-3 clusters. We have calculated the absorption spectrum of Ca around the 4s4p <- 4s(2) transition and have found that it is bluesh…
Unconventional phases of attractive Fermi gases in synthetic Hall ribbons
2017
An innovative way to produce quantum Hall ribbons in a cold atomic system is to use M hyperfine states of atoms in a one-dimensional optical lattice to mimic an additional "synthetic dimension." A notable aspect here is that the SU(M) symmetric interaction between atoms manifests as "infinite ranged" along the synthetic dimension. We study the many-body physics of fermions with SU(M) symmetric attractive interactions in this system using a combination of analytical field theoretic and numerical density-matrix renormalization-group methods. We uncover the rich ground-state phase diagram of the system, including unconventional phases such as squished baryon fluids, shedding light on many-body…