The European Physical Journal D最新文献

The quantum defect theory (QDT) has been successfully used to describe processes involving high-excited (Rydberg) states of atoms and molecules with a single valence electron over closed shells. This study proposes a modification of QDT to describe the low-energy excited states of a more complex atom (oxygen) which are responsible for its infrared (IR) spectrum. The radial wavefunctions of low-excited electron states include the quantum defect dependence on energy which is derived from the whole spectral series, in contrast to the highly excited Rydberg levels, whose quantum defects are determined by the individual level energies. Our method was applied to calculate the transition probabilities in the neutral oxygen spectra in discharge plasma measured using high-resolution time-resolved IR Fourier transform spectroscopy. The Boltzmann plots resulting from the experimental spectra prove that the modified QDT approach is an adequate method for calculating atomic dipole transition moments.

We revisit the coherent population trapping (CPT) of a three-state system in the presence of environmental fluctuations and strong electromagnetic driving fields. To this end, we use a fluctuation-regulated quantum master equation that considers the drive-induced dissipation (DID) in the system. The DID originates from the combined effect of a driving field and environmental fluctuations. We report that increasing DID shows a narrowing of CPT linewidth and, hence, improved selection of the dark states. As such, the DID enhances the sensitivity of CPT at a driving strength much larger than the system’s relaxation rates. We also discuss the practical implementation of the scheme along with possible applications.

The figure shows the narrowing of CPT responance (narrow dark region) as the environmental fluctuation correlation (tau _c) and hence, the drive-induced dissipation increases.

We revisit the Bose–Hubbard model with hard-core three-body attractive interactions in one-dimension using the cluster mean-field theory with the density-matrix renormalization group. Our study focuses on the region of the phase diagram between density one Mott MI(1) and density three Mott MI(3) insulator lobes and studies the pairing of bosons. We calculate the order parameters and condensate factors corresponding to atomic and pair superfluid phases. We find no phase transition directly from MI(1) to MI(3) when the attractive three-body interaction is present. The pair superfluid dominates the region between MI(1) and MI(3) when the hopping parameter is small. As the hopping parameter increases, the model shows a phase transition to the atomic superfluid. However, the paring of bosons persists even in the atomic superfluid phases. We finally obtain the phase diagram and compare it with earlier results.

To help the physicians, intra-cavity absorption spectroscopy is being used to design a highly sensitive biomedical sensor for air coming from the lungs. Using the principles of lasing, two different wavelengths (modes) are used to set up this operation. An analysis of our previous results indicates that an in-depth investigation of the fibre Bragg gratings is mandatory which has been done in this work. As the sensor’s operation relies heavily on these FBGs, we resort to calculate and investigate their Bragg wavelengths in accordance with the respective intrinsic properties and data-sheets. Each FBG has been characterized rigorously under numerous temperature conditions for long periods of time and leads to the design limitations of the Bragg wavelength. Afterwards, an intensive measurement and evaluation of signal-to-noise ratio of both modes with respect to the input parameters of the setup is performed. This excessive investigation leads to an increased value of signal-to-noise ratio of 54.5 dB in comparison to previous work and profound implementation attributes that have been discussed in detail.

The 5S(rightarrow )6P transition in rubidium (Rb) at 420 nm offers the advantage of narrow linewidth and diverse applications in quantum technologies. However, the direct spectroscopy at this transition is challenging due to its weak transition strength. In this paper, we have discussed the saturated absorption spectroscopy (SAS) of Rb using the narrow-line transition at 420 nm. We have studied the effect of the temperature of the Rb cell, control beam power, and beam size on the SAS dip heights and their linewidths. Additionally, our study offers a comprehensive examination, encompassing all eight error signals of Rb for the 5 S(rightarrow )6P transition at 420 nm and 421 nm. These findings contribute valuable insights to the field of laser frequency stabilization of Rb at blue transition and can be useful in quantum technologies based on this transition.

Direct spectroscopy of Rubidium at blue transition.

Atom and, of late, molecule interferometers find application in both the crucible of fundamental research and industrial pursuits. A prevalent methodology in the construction of atom interferometers involves the utilisation of gratings fashioned from laser beams. While this approach imparts commendable precision, it is hampered by its incapacity to attain exceedingly short wavelengths and its dependence on intricate laser systems for operational efficacy. All applications require the control of matter waves, particularly the particle’s velocity. In this manuscript, we propose a continuous beam monochromator scheme reaching enormously high velocity purification with speed ratios in the order of (10^3) based on atom-surface diffraction. Beyond these high purifications, the proposed scheme simplifies the application by reducing the degree of freedom to a single angle, selecting the wanted particle’s velocity.

Orthogonal operators are a next step in the semi-empirical description of complex spectra. Orthogonality yields optimal independence and thus least correlation between the operators. The increased stability of the fitting process is used to include higher-order many-body as well as fully relativistic effects. The calculated eigenvalues are frequently an order of magnitude more accurate with respect to a conventional semi-empirical approach. The resulting eigenvectors may not only be put to use to calculate transition probabilities and g-factors, but also to calculate hyperfine structure A and B constants. We illustrate our first steps in this field with two examples of first spectra of the iron group elements. The results are compared to current experimental hyperfine structure A-values while strong and weak points of the method are discussed. In particular to be able to deal with lanthanides and actinides, the orthogonal operator method is completed with the definition of operators for equivalent p- and f-electrons.