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arXiv2018

Experimental and theoretical study of the B(2)$^2 Σ^+ \rightarrow$ X(1)$^2 Σ^+$ system in the KSr molecule

Spectral bands for the B(2)$^{2}Σ^{+}\rightarrow$ X(1)$^{2}Σ^{+}$ electronic transition in the doubly-polar open-shell KSr molecule are recorded at moderate resolution using the thermoluminescence technique. The spectra are simulated using three kinds of advanced electronic structure calculations, allowing for an assessment of their accuracy on one hand, and for the derivation of fundamental spectroscopic constants of the X(1)$^{2}Σ^{+}$ KSr ground state and the excited electronic state B(2)$^{2}Σ^{+}$, on the other hand. These results should facilitate further studies aiming at creating ultracold bosonic or fermionic KSr molecules.

physics.atom-ph↗

arXiv2018

Extended calculations of energy levels, radiative properties, $A_{J}$, $B_{J}$ hyperfine interaction constants, and Landé $g_{J}$-factors for nitrogen-like \mbox{Ge XXVI}

Employing two state-of-the-art methods, multiconfiguration Dirac--Hartree--Fock and second-order many-body perturbation theory, highly accurate calculations are performed for the lowest 272 fine-structure levels arising from the $2s^{2} 2p^{3}$, $2s 2p^{4}$, $2p^{5}$, $2s^{2} 2p^{2} 3l$~($l=s,p,d$), $2s 2p^{3}3l$ ($l=s,p,d$), and $2p^{4} 3l$ ($l=s,p,d$) configurations in nitrogen-like Ge XXVI. Complete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé $g_{J}$-factors, and E1, E2, M1, M2 line strengths, oscillator strengths, and transition rates among these 272 levels are provided. Comparisons are made between the present two data sets, as well as with other available experimental and theoretical values. The present data are accurate enough for identification and deblending of emission lines involving the $n=3$ levels, and are also useful for modeling and diagnosing fusion plasmas.

physics.atom-ph↗

arXiv2014

Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter

The Thorium-229 isotope features a nuclear isomer state with an extremely low energy. The currently most accepted energy value, 7.8 +- 0.5 eV, was obtained from an indirect measurement using a NASA x-ray microcalorimeter with an instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic microcalorimeters with an energy resolution down to a few eV can be used to measure the isomer energy. In particular, resolving the 29.18 keV doublet in the γ-spectrum following the α-decay of Uranium-233, corresponding to the decay into the ground and isomer state, allows to measure the isomer transition energy without additional theoretical input parameters, and increase the energy accuracy. We study the possibility of resolving the 29.18 keV line as a doublet and the dependence of the attainable precision of the energy measurement on the signal and background count rates and the instrumental resolution.

physics.atom-ph↗

arXiv2014

Photostimulated phosphor based image plate detection system for HRVUV beamline at Indus-1 synchrotron radiation source

A high resolution vacuum ultraviolet (HRVUV) beamline based on a 6.65 meter off-plane Eagle spectrometer is in operation at the Indus-1 synchrotron radiation source, RRCAT, Indore, India. To facilitate position sensitive detection and fast spectral recording, a new BaFBr:Eu2+ phosphor based image plate (IP) detection system interchangeable with the existing photomultiplier (PMT) scanning system has been installed on this beamline. VUV photoabsorption studies on Xe, O2, N2O and SO2 are carried out to evaluate the performance of the IP detection system. An FWHM of ~ 0.5 Å is achieved for the Xe atomic line at 1469.6 Å. Reproducibility of spectra is found to be within the experimental resolution. Compared to the PMT scanning system, the IP shows several advantages in terms of sensitivity, recording time and S/N ratio, which are highlighted in the paper. This is the first report of incorporation of an IP detection system in a VUV beamline using synchrotron radiation. Commissioning of the new detection system is expected to greatly enhance the utilization of the HRVUV beamline as a number of spectroscopic experiments which require fast recording times combined with a good signal to noise ratio are now feasible.

physics.ins-det↗

arXiv2018

A Facility for Production and Laser Cooling of Cesium Isotopes and Isomers

We report on the design, installation, and test of an experimental facility for the production of ultra-cold atomic isotopes and isomers of cesium. The setup covers a broad span of mass numbers and nuclear isomers, allowing one to directly compare chains of isotopes and isotope/isomer pairs. Cesium nuclei are produced by fission or fusion-evaporation reactions using primary proton beams from a 130 MeV cyclotron impinging upon a suitable target. The species of interest is ejected from the target in ionic form, electrostatically accelerated, mass separated, and routed to a science chamber. Here, ions are neutralized by implantation in a thin foil, and extracted by thermal diffusion. A neutral vapor at room temperature is thus formed and trapped in a magneto-optical trap. Real-time fluorescence imaging and destructive absorption imaging provide information on the number of trapped atoms, their density, and their temperature. Tests with a dedicated beam of $^{133}$Cs$^{+}$ ions at 30 keV energy confirm neutralization, evaporation, and laser cooling to 150 $μ$K, with an average atomic density of 10$^{10}$ cm$^{-3}$. Availability of cold and dense atomic samples of Cs isotopes and isomers opens new avenues for high-precision measurements of isotopic and isomeric shifts thereby gaining deeper insight into the nuclear structure, as well as for sensitive measurements of isotopes' concentration ratios in trace quantities. The facility also constitutes the core for future experiments of many-body physics with nuclear isomers.

physics.ins-det↗

arXiv2013

Kinetics of polarization in non-relativistic scattering

An approach is developed, which essentially simplifies derivation of kinetic equation for polarization in non-relativistic scattering. This approach is applicable for collision of projectile particles with a target for any spins of colliding particles. The most detailed consideration is performed for the case of spin 1/2 projectile particle interacting with spin 1/2 particle of a target. The solution of the kinetic equation for the case of zero initial polarization is presented.

physics.atom-ph↗

arXiv2019

Eta Decay and Muonic Puzzles

New physics motivated by muonic puzzles (proton radius and muon $g-2$ discrepancies) is studied. Using a light scalar boson $ϕ$, assuming Yukawa interactions, accounts for these muonic puzzles simultaneously. Our previous work limits the existence of such a scalar boson's mass $m_ϕ$ from about 160 keV to 60 MeV. We improve this result by including the influence of all of the possible particles that couple to the $ϕ$ in computing the decay rate. Doing this involves including the strong interaction physics, involving quarks, necessary to compute the $ηπϕ$ vertex function. The Nambu-Jona-Lasinio model, which accounts for the spontaneous symmetry breaking that yields the constituent mass is employed to represent the relevant strong-interaction physics. We use the $ηπϕ$ vertex function to reanalyze the electron beam dump experiments. The result is that the allowed range of $m_ϕ$ lies between about 160 keV and 3.5 MeV. This narrow range represents an inviting target for ruling out or discovering this scalar boson. A possible UV completion of our phenomenological model is discussed.

hep-ph↗

arXiv2014

Propagation of two short laser pulse trains in a $Λ$-type three-level medium under conditions of electromagnetically induced transparency

We investigate the dynamics of a pair of short laser pulse trains propagating in a medium consisting of three-level $Λ$-type atoms by numerically solving the Maxwell-Schrödinger equations for atoms and fields. By performing propagation calculations with different parameters, under conditions of electromagnetically induced transparency, we compare the propagation dynamics by a single pair of probe and coupling laser pulses and by probe and coupling laser pulse trains. We discuss the influence of the coupling pulse area, number of pulses, and detunings on the probe laser propagation and realization of electromagnetically induced transparency conditions, as well on the formation of a dark state.

physics.atom-ph↗

arXiv2018

Competition effects of multiple quantum paths in an atom interferometer

We present an observation of competition effect among multiple quantum paths in a Raman-type Mach-Zehnder atom interferometer. By measuring the contrast of interference fringes, the competition effect among multiple interference paths is experimentally investigated. Due to the phase competition, the contrast periodically oscillates when modulating either the phase or the interrogation time between Raman pulses. The multiple quantum paths form because of the imperfect population transfer efficiency in stimulated Raman transitions, and are verified by modulating the duration of Raman pulses. The contrast could be optimized by suppressing the phase competition.

physics.atom-ph↗

arXiv2018

Photon-photon correlations with a V-type three-level system interacting with two quantized field modes

We carry out a model study on the interaction of a $V$-type three-level emitter with two quantized cavity modes which are weakly driven by two classical fields. The emitter may be an atom or a molecule with nondegenerate upper levels in general. The lifetimes of the two upper levels are assumed to be much longer than the lifetime of the cavity photons. We calculate the two-time second order coherence function, namely Hanbury Brown-Twiss function $g^{(2)}(τ)$ where $τ$ is the time delay between the two modes. We analyze the photon-photon correlations between the two cavity modes in terms of $g^{(2)}(τ)$. The variation of $g^{(2)}(τ)$ as a function of $τ$ exhibits collapse and revival type oscillations as well as quantum beats for relatively short $τ$ while in the limit $τ\rightarrow \infty$, $g^{(2)}(τ) \simeq 1$. We further show that the two cavity field modes are entangled when $g^{(2)}(0) > 2$. We develop a dressed state picture with single photon in each mode to explain the results and use the negativity of the partial transpose of the reduced field density matrix to show the entanglement between field modes. The model presented in this paper may be useful for generating entangled photon pairs, and also manipulating photon-photon correlations with a cavity QED set up.

physics.atom-ph↗

arXiv2019

Diffraction of a partial temporal coherent beam from a single-slit and a circular aperture

We generalize the notion of the Franhoufer diffraction from a single slit and a circular aperture to the case of partially temporal coherent and quasimonochromatic light. The problem is studied analytically and the effect of coherence length on the diffraction pattern is investigated. In this case the far-field distribution of the irradiance depends on the newly introduced parameter(decoherence parameter) which governs the deviation of the diffraction pattern from the usual one. The corrections due to temporal decoherency on the irradiance distribution in the far field is obtained. Numerical study of the effect of decoherence parameter on the Far-field diffraction pattern is performed. In the case of a single slit, there is no noticeable deviation in the central peak, but in the higher orders of diffraction, deviation become apparent. For circular apertures, as long as the decoherence parameter is greater than one , the beam decoherency affects the distribution profile and the first order diffraction pattern decreases and by increasing the decoherence parameter, the first order of diffraction pattern gradually disappears.

physics.optics↗

arXiv2021

Quench dynamics of two interacting atoms in a one-dimensional anharmonic trap

A temporal response of two interacting particles to a quench of the coupling strength in one-dimensional harmonic and anharmonic traps is explored. The coupling strength is changed from repulsive to attractive interactions and vice versa. The time evolution of the fidelity, wave packet, one-body reduced density matrix and momentum distributions is analyzed in details. It was found that impacts of the pre- and postquench states interchange during the dynamics. In the case of the anharmonic trap additional contribution of the center-of-mass excited states comes into play and the whole evolution becomes significantly altered. Yet the impact of the pre- and postquench states in some cases still could be identified. The quench dynamics of the ground and excited states are considered.

physics.atom-ph↗

arXiv2018

Coupling field dependent quantum interference effects in a $Λ$-system of $^{87}Rb$ atom

A $Λ$-system in $D_2$ line transition of the $^{87}Rb$ atom has been investigated for quantum interference effects for different configurations of coupling field. With a travelling wave coupling field (co-propagating with probe field), the probe beam shows the earlier known electromagnetically induced transparency (EIT) effect at the resonance. With a standing wave coupling field (which is co- and counter-propagating with probe beam), the probe EIT gets transformed into an electromagnetically induced absorption (EIA). A variation in coupling beam power has shown that, at high coupling power, EIA signals have much larger amplitude and slope than those of EIT signals with and without applied magnetic field. These EIA signals can be useful for tight laser frequency locking and optical switching.

physics.atom-ph↗

arXiv2018

Study of EIT resonances in an anti-relaxation coated Rb vapor cell

We demonstrate---experimentally and theoretically---that resonances obtained in electromagnetically induced transparency (EIT) can be both bright and dark. The experiments are done using magnetic sublevels of a hyperfine transition in the D$_1$ line of $^{87}$Rb. The degeneracy of the sublevels is removed by having a magnetic field of value 27 G. The atoms are contained in a room-temperature vapor cell with anti-relaxation coating on the walls. Theoretical analysis based on a two-region model reproduces the experimental spectrum quite well. This ability to have both bright and dark resonances promises applications in sub- and super-luminal propagation of light, and sensitive magnetometry.

physics.atom-ph↗

arXiv2019

On the weakly-bound (1,1)-states in the three-body $d d μ$ and $d t μ$ muonic ions

The both total and binding energies of the (1,1)-states in the weakly-bound three-body muonic $d d μ$ and $d t μ$ ions are determined to high numerical accuracy. The binding energy of the (1,1)-state in the muonic $d t μ$ ion is evaluated as $\varepsilon(d t μ)$ = -0.66033003831(30) $eV$, while for the same state in the muonic $d d μ$ ion we have found that $\varepsilon(d d μ)$ = -1.9749806166970(30) $eV$. These energies are the most accurate numerical values obtained for these systems and they are sufficient for all current and future experimental needs.

physics.atom-ph↗

arXiv2014

New Precision Measurement of Hyperfine Splitting of Positronium

The ground state hyperfine splitting of positronium $Δ_{\mathrm{HFS}}$ is sensitive to high order corrections of quantum electrodynamics (QED) in bound state. The theoretical prediction and the averaged experimental value for $Δ_{\mathrm{HFS}}$ has a discrepancy of 15 ppm, which is equivalent to 3.9 standard deviations (s.d.). A new precision measurement which reduces the systematic uncertainty from the positronium thermalization effect was performed, in which the non-thermalization effect was measured to be as large as $10 \pm 2\,{\mathrm{ppm}}$ in a timing window we used. When this effect is taken into account, our new result becomes $Δ_{\mathrm{HFS}} = 203.394\,2 \pm 0.001\,6 ({\mathrm{stat., 8.0\,ppm}}) \pm 0.001\,3 ({\mathrm{sys., 6.4\,ppm}})$\,GHz, which favors the QED prediction within 1.2 s.d. and disfavors the previous experimental average by 2.6 s.d.

hep-ex↗

arXiv2014

Improved estimates of the nuclear structure corrections in $μ$D

We calculate the nuclear structure corrections to the Lamb shift in muonic deuterium by using state-of-the-art nucleon-nucleon potentials derived from chiral effective field theory. Our calculations complement previous theoretical work obtained from phenomenological potentials and the zero range approximation. The study of the chiral convergence order-by-order and the dependence on cutoff variations allows us to improve the estimates on the nuclear structure corrections and the theoretical uncertainty coming from nuclear potentials. This will enter the determination of the nuclear radius from ongoing muonic deuterium experiments at PSI.

nucl-th↗

arXiv2014

A measurement of the neutron to 199Hg magnetic moment ratio

The neutron gyromagnetic ratio has been measured relative to that of the 199Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in the same volume and report the result $γ_{\rm n}/γ_{\rm Hg} = 3.8424574(30)$.

nucl-ex↗