@article{14845,
  abstract     = {We study a linear rotor in a bosonic bath within the angulon formalism. Our focus is on systems where isotropic or anisotropic impurity-boson interactions support a shallow bound state. To study the fate of the angulon in the vicinity of bound-state formation, we formulate a beyond-linear-coupling angulon Hamiltonian. First, we use it to study attractive, spherically symmetric impurity-boson interactions for which the linear rotor can be mapped onto a static impurity. The well-known polaron formalism provides an adequate description in this limit. Second, we consider anisotropic potentials, and show that the presence of a shallow bound state with pronounced anisotropic character leads to a many-body instability that washes out the angulon dynamics.},
  author       = {Dome, Tibor and Volosniev, Artem and Ghazaryan, Areg and Safari, Laleh and Schmidt, Richard and Lemeshko, Mikhail},
  issn         = {2469-9969},
  journal      = {Physical Review B},
  number       = {1},
  publisher    = {American Physical Society},
  title        = {{Linear rotor in an ideal Bose gas near the threshold for binding}},
  doi          = {10.1103/PhysRevB.109.014102},
  volume       = {109},
  year         = {2024},
}

@article{294,
  abstract     = {We developed a method to calculate two-photon processes in quantum mechanics that replaces the infinite summation over the intermediate states by a perturbation expansion. This latter consists of a series of commutators that involve position, momentum, and Hamiltonian quantum operators. We analyzed several single- and many-particle cases for which a closed-form solution to the perturbation expansion exists, as well as more complicated cases for which a solution is found by convergence. Throughout the article, Rayleigh and Raman scattering are taken as examples of two-photon processes. The present method provides a clear distinction between the Thomson scattering, regarded as classical scattering, and quantum contributions. Such a distinction lets us derive general results concerning light scattering. Finally, possible extensions to the developed formalism are discussed.},
  author       = {Fratini, Filippo and Safari, Laleh and Amaro, Pedro and Santos, José},
  journal      = {Physical Review A - Atomic, Molecular, and Optical Physics},
  number       = {4},
  publisher    = {American Physical Society},
  title        = {{Two-photon processes based on quantum commutators}},
  doi          = {10.1103/PhysRevA.97.043842},
  volume       = {97},
  year         = {2018},
}

@article{427,
  abstract     = {We investigate the quantum interference induced shifts between energetically close states in highly charged ions, with the energy structure being observed by laser spectroscopy. In this work, we focus on hyperfine states of lithiumlike heavy-Z isotopes and quantify how much quantum interference changes the observed transition frequencies. The process of photon excitation and subsequent photon decay for the transition 2s→2p→2s is implemented with fully relativistic and full-multipole frameworks, which are relevant for such relativistic atomic systems. We consider the isotopes Pb79+207 and Bi80+209 due to experimental interest, as well as other examples of isotopes with lower Z, namely Pr56+141 and Ho64+165. We conclude that quantum interference can induce shifts up to 11% of the linewidth in the measurable resonances of the considered isotopes, if interference between resonances is neglected. The inclusion of relativity decreases the cross section by 35%, mainly due to the complete retardation form of the electric dipole multipole. However, the contribution of the next higher multipoles (e.g., magnetic quadrupole) to the cross section is negligible. This makes the contribution of relativity and higher-order multipoles to the quantum interference induced shifts a minor effect, even for heavy-Z elements.},
  author       = {Amaro, Pedro and Loureiro, Ulisses and Safari, Laleh and Fratini, Filippo and Indelicato, Paul and Stöhlker, Thomas and Santos, José},
  journal      = { Physical Review A - Atomic, Molecular, and Optical Physics},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Quantum interference in laser spectroscopy of highly charged lithiumlike ions}},
  doi          = {10.1103/PhysRevA.97.022510},
  volume       = {97},
  year         = {2018},
}

@article{1496,
  abstract     = {The two-photon 1s2 2s 2p 3P0 1s22s2 1S0 transition in berylliumlike ions is theoretically investigated within a fully relativistic framework and a second-order perturbation theory. We focus our analysis on how electron correlation, as well as the negative-energy spectrum, can affect the forbidden E1M1 decay rate. For this purpose, we include the electronic correlation via an effective local potential and within a single configuration-state model. Due to its experimental interest, evaluations of decay rates are performed for berylliumlike xenon and uranium. We find that the negative-energy contribution can be neglected at the present level of accuracy in the evaluation of the decay rate. On the other hand, if contributions of electronic correlation are not carefully taken into account, it may change the lifetime of the metastable state by up to 20%. By performing a full-relativistic jj-coupling calculation, we found a decrease of the decay rate by two orders of magnitude compared to non-relativistic LS-coupling calculations, for the selected heavy ions.},
  author       = {Amaro, Pedro and Fratini, Filippo and Safari, Laleh and Machado, Jorge and Guerra, Mauro and Indelicato, Paul and Santos, José},
  journal      = {Physical Review A - Atomic, Molecular, and Optical Physics},
  number       = {3},
  publisher    = {American Physical Society},
  title        = {{Relativistic evaluation of the two-photon decay of the metastable 1s22s2p3P0 state in berylliumlike ions with an effective-potential model}},
  doi          = {10.1103/PhysRevA.93.032502},
  volume       = {93},
  year         = {2016},
}

@article{1693,
  abstract     = {Quantum interference between energetically close states is theoretically investigated, with the state structure being observed via laser spectroscopy. In this work, we focus on hyperfine states of selected hydrogenic muonic isotopes, and on how quantum interference affects the measured Lamb shift. The process of photon excitation and subsequent photon decay is implemented within the framework of nonrelativistic second-order perturbation theory. Due to its experimental interest, calculations are performed for muonic hydrogen, deuterium, and helium-3. We restrict our analysis to the case of photon scattering by incident linear polarized photons and the polarization of the scattered photons not being observed. We conclude that while quantum interference effects can be safely neglected in muonic hydrogen and helium-3, in the case of muonic deuterium there are resonances with close proximity, where quantum interference effects can induce shifts up to a few percent of the linewidth, assuming a pointlike detector. However, by taking into account the geometry of the setup used by the CREMA collaboration, this effect is reduced to less than 0.2% of the linewidth in all possible cases, which makes it irrelevant at the present level of accuracy. © 2015 American Physical Society.},
  author       = {Amaro, Pedro and Franke, Beatrice and Krauth, Julian and Diepold, Marc and Fratini, Filippo and Safari, Laleh and Machado, Jorge and Antognini, Aldo and Kottmann, Franz and Indelicato, Paul and Pohl, Randolf and Santos, José},
  journal      = {Physical Review A},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Quantum interference effects in laser spectroscopy of muonic hydrogen, deuterium, and helium-3}},
  doi          = {10.1103/PhysRevA.92.022514},
  volume       = {92},
  year         = {2015},
}

@article{1811,
  abstract     = {Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.},
  author       = {Safari, Laleh and Santos, José and Amaro, Pedro and Jänkälä, Kari and Fratini, Filippo},
  journal      = {Journal of Mathematical Physics},
  number       = {5},
  publisher    = {American Institute of Physics},
  title        = {{Analytical evaluation of atomic form factors: Application to Rayleigh scattering}},
  doi          = {10.1063/1.4921227},
  volume       = {56},
  year         = {2015},
}

@article{1587,
  abstract     = {We investigate the quantum interference shifts between energetically close states, where the state structure is observed by laser spectroscopy. We report a compact and analytical expression that models the quantum interference induced shift for any admixture of circular polarization of the incident laser and angle of observation. An experimental scenario free of quantum interference can thus be predicted with this formula. Although this study is exemplified here for muonic deuterium, it can be applied to any other laser spectroscopy measurement of ns-n′p frequencies of a nonrelativistic atomic system, via an ns→n′p→n′′s scheme.},
  author       = {Amaro, Pedro and Fratini, Filippo and Safari, Laleh and Antognini, Aldo and Indelicato, Paul and Pohl, Randolf and Santos, José},
  journal      = {Physical Review A - Atomic, Molecular, and Optical Physics},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Quantum interference shifts in laser spectroscopy with elliptical polarization}},
  doi          = {10.1103/PhysRevA.92.062506},
  volume       = {92},
  year         = {2015},
}

@article{1995,
  abstract     = {Optical transport represents a natural route towards fast communications, and it is currently used in large scale data transfer. The progressive miniaturization of devices for information processing calls for the microscopic tailoring of light transport and confinement at length scales appropriate for upcoming technologies. With this goal in mind, we present a theoretical analysis of a one-dimensional Fabry-Perot interferometer built with two highly saturable nonlinear mirrors: a pair of two-level systems. Our approach captures nonlinear and nonreciprocal effects of light transport that were not reported previously. Remarkably, we show that such an elementary device can operate as a microscopic integrated optical rectifier.},
  author       = {Fratini, Filippo and Mascarenhas, Eduardo and Safari, Laleh and Poizat, Jean and Valente, Daniel and Auffèves, Alexia and Gerace, Dario and Santos, Marcelo},
  journal      = {Physical Review Letters},
  number       = {24},
  publisher    = {American Physical Society},
  title        = {{Fabry-Perot interferometer with quantum mirrors: Nonlinear light transport and rectification}},
  doi          = {10.1103/PhysRevLett.113.243601},
  volume       = {113},
  year         = {2014},
}