# Sergey G. PorsevUniversity of Delaware | UDel UD · Department of Physics and Astronomy

Sergey G. Porsev

Ph.D.

## About

183

Publications

21,128

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6,130

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Introduction

Additional affiliations

February 1987 - present

Education

September 1981 - February 1987

## Publications

Publications (183)

We introduce the pCI software package for high-precision atomic structure calculations. The standard method of calculation is based on the configuration interaction (CI) method to describe valence correlations, but can be extended to attain better accuracy by including core correlations via many-body perturbation theory (CI+MBPT) or the all-order (...

In state-of-the-art optical lattice clocks, beyond-electric-dipole polarizability terms lead to a break-down of magic wavelength trapping. In this Letter, we report a novel approach to evaluate lattice light shifts, specifically addressing recent discrepancies in the atomic multipolarizability term between experimental techniques and theoretical ca...

We propose In-like Pr10+ as a candidate for the development of a high-accuracy optical clock with high sensitivity to a time variation of the fine-structure constant, (\dot alpha}/alpha, as well as favorable experimental systematics. We calculate its low-lying energy levels by combining the configuration interaction and the coupled cluster method,...

Optical atomic clocks are the most accurate and precise measurement devices of any kind, enabling advances in international timekeeping, Earth science, fundamental physics, and more. However, there is a fundamental tradeoff between accuracy and precision, where higher precision is achieved by using more atoms, but this comes at the cost of larger i...

We report on the coherent excitation of the ultranarrow S 0 1 – P 2 3 magnetic quadrupole transition in Sr 88 . By confining atoms in a state insensitive optical lattice, we achieve excitation fractions of 97(1)% and observe linewidths as narrow as 58(1) Hz. With Ramsey spectroscopy, we find coherence times of 14(1) ms, which can be extended to 266...

We used the monochromatic soft-x-ray beamline P04 at the synchrotron-radiation facility PETRA III to resonantly excite the strongest 2 p − 3 d transitions in neonlike Ni ions, [ 2 p 6 ] J = 0 → [ ( 2 p 5 ) 1 / 2 3 d 3 / 2 ] J = 1 and [ 2 p 6 ] J = 0 → [ ( 2 p 5 ) 3 / 2 3 d 5 / 2 ] J = 1 , respectively dubbed 3 C and 3 D , achieving a resolving powe...

Divalent atoms and ions with a singlet S ground state and triplet P excited state form the basis of many high-precision optical atomic clocks. Along with the metastable P03 clock state, these atomic systems also have a nearby metastable P23 state. We investigate the properties of the electric quadrupole 1S0↔P23 transition with a focus on enhancing...

We address the problem of lattice light shifts in the Sr clock caused by multipolar M1 and E2 atom-field interactions. We present a simple but accurate formula for the magnetic-dipole polarizability that takes into account the contributions of both the positive- and negative-energy states. We calculate the contribution of negative-energy states to...

Divalent atoms and ions with a singlet $S$ ground state and triplet $P$ excited state form the basis of many high-precision optical atomic clocks. Along with the metastable $^{3}\mathrm{P}_{0}$ clock state, these atomic systems also have a nearby metastable $^{3}\mathrm{P}_{2}$ state. We investigate the properties of the electric quadrupole $^{1}\m...

We address the problem of lattice light shifts in the Sr clock caused by multipolar M1 and E2 atom-field interactions. We presented a simple but accurate formula for the magnetic-dipole polarizability that takes into account both the positive and negative energy states contributions. We calculated the contribution of negative energy states to the M...

We propose an optical clock based on ultranarrow transitions in neutral titanium, which exhibit small blackbody radiation and quadratic Zeeman shifts and have wavelengths in the S-, C-, and L-telecommunications fiber bands, allowing for integration with robust laser technology. We calculate relevant properties using a high-precision relativistic hy...

We propose an optical clock based on narrow, spin-forbidden M1 and E2 transitions in laser-cooled neutral titanium. These transitions exhibit much smaller black body radiation shifts than those in alkaline earth atoms, small quadratic Zeeman shifts, and have wavelengths in the S, C, and L-bands of fiber-optic telecommunication standards, allowing f...

We show that coupling of ultralight dark matter (UDM) to quarks and gluons would lead to an oscillation of the nuclear charge radius for both the quantum chromodynamics (QCD) axion and scalar dark matter. Consequently, the resulting oscillation of electronic energy levels could be resolved with optical atomic clocks, and their comparisons can be us...

One of the most enduring and intensively studied problems of x-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power 2...

We carried out calculations of the energies and magnetic dipole hyperfine-structure constants of the low-lying states of U+233 and U233 using two different approaches. With six valence electrons and a very heavy core, uranium represents a major challenge for precision atomic theory even using large-scale computational resources. The first approach...

We propose a many-ion optical atomic clock based on three-dimensional Coulomb crystals of order one thousand Sn$^{2+}$ ions confined in a linear RF Paul trap. Sn$^{2+}$ has a unique combination of features that is not available in previously considered ions: a $^1$S$_0$ $\leftrightarrow$ $^3$P$_0$ clock transition between two states with zero elect...

We carried out calculations of the energies and magnetic dipole hyperfine structure constants of the low-lying states of 233U^+ and 233U using two different approaches. With six valence electrons and a very heavy core, uranium represents a major challenge for precision atomic theory even using large-scale computational resources. The first approach...

Here we report measured and calculated values of decay rates of the 3d4(D5)4s4p(Po3)yP2,3,4o7 states of Cr i. The decay rates are measured using time-correlated single-photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for transitions between these states and the ground state are measured by laser induced fluorescenc...

One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two ubiquitous Fe{~\sc XVII} transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA~III synchrotron facility by increasing the...

Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work, we improve the precision of such a method by including for the first time an iterative solution of equations for the core triple cluste...

Here we report measured and calculated values of decay rates of the 3d$^4$($^5$D)4s4p($^3$P$^{\rm{o}}$)\ y$^7$P$^{\rm{o}}_{2,3,4}$ states of Cr I. The decay rates are measured using time-correlated single photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for these transitions are measured by laser induced fluorescen...

Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster a...

The nuclear transition between the ground and the low-energy isomeric state in the ²²⁹ Th nucleus is of interest due to its high sensitivity to a hypothetical temporal variation of the fundamental constants and a possibility to build a very precise nuclear clock, but precise knowledge of the nuclear clock transition frequency is required. In this w...

The nuclear transition between the ground and the low-energy isomeric state in the ^{229}Th nucleus is of interest due to its high sensitivity to a hypothetical temporal variation of the fundamental constants and a possibility to build a very precise nuclear clock, but precise knowledge of the nuclear clock transition frequency is required. In this...

We carried out calculations of the energies, hyperfine structure constants, and electric-dipole transition amplitudes for the low-lying states of Ba+ in the framework of the relativistic linearized coupled-cluster single double and coupled-cluster single double (valence) triple methods. Taking into account that an iterative inclusion of the valence...

High precision atomic data are indispensable for studies of fundamental symmetries, tests of fundamental physics postulates, developments of atomic clocks, ultracold atom experiments, astrophysics, plasma science, and many other fields of research. We have developed a new parallel atomic structure code package that enables computations that were no...

High precision atomic data is indispensable for experiments involving studies of fundamental interactions, astrophysics, atomic clocks, plasma science, and others. We develop new parallel atomic structure codes and explore the difficulties of load-balancing in these codes. Efficient load-balancing of matrix elements for many-electron systems is ver...

We carried out calculations of the energies, hyperfine structure constants and electric-dipole transiton amplitudes for the low-lying states of Ba+ in the framework of the relativistic linearized coupled-cluster single double (LCCSD) and coupled-cluster single double (valence) triple (CCSDvT) methods. Taking into account that an iterative inclusion...

Two lowest-energy odd-parity atomic levels of actinium, 7s27p2Po1/2, 7s27p2Po3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) and 12276.59(2) cm−1. The lifetimes of these states were determined as 668(11) and 255(7) ns, respectively. In addition, we observed the effe...

In the recent work by Yamaguchi et al. [Phys. Rev. Lett. 123, 113201 (2019)] Cd was identified as an excellent candidate for a lattice clock. Here, we carried out computations needed for further clock development and made an assessment of the higher-order corrections to the light shift of the 5s2 S01−5s5p P0o3 clock transition. We carried out calcu...

Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly charged ions (HCIs) made HCIs accessible for high-resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in...

For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic 2p−3d transitions, 3C and 3D, in Fe XVII ions found oscillator strength ratios f(3C)/f(3D) disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lin...

We demonstrate state-dependent optical lattices for the Sr optical qubit at the tune-out wavelength for its ground state. We tightly trap excited state atoms while suppressing the effect of the lattice on ground state atoms by more than 4 orders of magnitude. This highly independent control over the qubit states removes inelastic excited state coll...

Two lowest-energy odd-parity atomic levels of actinium, 7s^27p 2P^o_1/2, 7s^27p 2P^o_3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) cm^-1 and 12 276.59(2) cm^-1. The lifetimes of these states were determined as 668(11) ns and 255(7) ns, respectively. In addition, t...

We develop a broadly applicable approach that drastically increases the ability to predict the properties of complex atoms accurately. We apply it to the case of Ir17+, which is of particular interest for the development of novel atomic clocks with a high sensitivity to the variation of the fine-structure constant and to dark matter searches. In ge...

Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly-charged ions (HCIs) made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in...

In the recent work [A.~Yamaguchi et. al, Phys. Rev. Lett. {\bf 123}, 113201 (2019)] Cd has been identified as an excellent candidate for a lattice clock. Here, we carried out computations needed for further clock development and made an assessment of the higher-order corrections to the light shift of the $5s^2\, ^1\!S_0$--$5s5p\, ^3\!P_0^o$ clock t...

We demonstrate state-dependent optical lattices for the Sr optical qubit at the tune-out wavelength for its ground state. We tightly trap excited state atoms while suppressing the effect of the lattice on ground state atoms by more than four orders of magnitude. This highly independent control over the qubit states removes inelastic excited state c...

We have developed a broadly-applicable approach that drastically increases the ability to accurately predict properties of complex atoms. We applied it to the case of Ir$^{17+}$, which is of particular interest for the development of novel atomic clocks with high sensitivity to the variation of the fine-structure constant and dark matter searches....

We report a measurement of the radium ion's 7pP3/22 state branching fractions and improved theoretical calculations. With a single laser-cooled 226Ra+ ion we measure the P3/2 branching fractions to the 7sS1/22 ground state 0.87678(20), the 6dD5/22 state 0.10759(10), and the 6dD3/22 state 0.01563(21).

We measured the L-shell soft X-ray fluorescence of Fe XVII ions in an electron beam ion trap following resonant photo-excitation using synchrotron radiation provided by the P04 beamline at PETRA III. Special attention is paid to two 2p-3d transitions, the 3C and 3D lines that are essential plasma diagnostics tools for astrophysics. Their resulting...

We have completed a measurement of the (6s26p2)P03→P23 939 nm electric quadrupole (E2) transition amplitude in atomic lead. Using a Faraday rotation spectroscopy technique and a sensitive polarimeter, we have measured this very weak E2 transition, and determined its amplitude to be 〈P23||Q||P03〉=8.91(9) a.u. We also present an ab initio theoretical...

We have completed a measurement of the $(6s^26p^2)\, ^3\!P_0 \rightarrow \, ^3\!P_2$ 939 nm electric quadrupole ($E2$) transition amplitude in atomic lead. Using a Faraday rotation spectroscopy technique and a sensitive polarimeter, we have measured this very weak $E2$ transition for the first time, and determined its amplitude to be $\langle ^3\!P...

We report the first measurement of the radium ion's $7p$ ${}^{2}P_{3/2}^o$ state branching fractions and improved theoretical calculations. With a single laser-cooled radium-226 ion we measure the $P_{3/2}$ branching fractions to the $7s$ ${}^{2}S_{1/2}$ ground state 0.87678(20), the $6d$ ${}^{2}D_{5/2}$ state 0.10759(10), and the $6d$ ${}^{2}D_{3/...

Questioning basic assumptions about the structure of space and time has greatly enhanced our understanding of nature. State-of-the-art atomic clocks 1–3 make it possible to precisely test fundamental symmetry properties of spacetime and search for physics beyond the standard model at low energies of just a few electronvolts ⁴ . Modern tests of Eins...

DOI:https://doi.org/10.1103/PhysRevA.99.029901

We measure the differential polarizability of the Lu+176 1S0↔3D1 clock transition at multiple wavelengths. This experimentally characterizes the differential dynamic polarizability for frequencies up to 372 THz and allows an experimental determination of the dynamic correction to the blackbody radiation shift for the clock transition. In addition,...

We demonstrate single-shot imaging and narrow-line cooling of individual alkaline-earth atoms in optical tweezers; specifically, strontium trapped in 515.2−nm light. Our approach enables high-fidelity detection of single atoms by imaging photons from the broad singlet transition while cooling on the narrow intercombination line, and we extend this...

Advances in laser spectroscopy of superheavy (Z>100) elements enabled determination of the nuclear moments of the heaviest nuclei, which required high-precision atomic calculations of the relevant hyperfine-structure (hfs) constants. Here, we calculated the hfs constants and energy levels for a number of nobelium (Z=102) states using a hybrid appro...

The isotope Th229 is unique in that it possesses an isomeric state of only a few electron volts above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear properties of both states have to be determined pre...

We measure the differential polarizability of the $^{176}$Lu$^+$ $^1S_0$ -to- ${^3}D_1$ clock transition at multiple wavelengths. This experimentally characterizes the differential dynamic polarizability for frequencies up to 372 THz and allows an experimental determination of the dynamic correction to the blackbody radiation shift for the clock tr...

Advances in laser spectroscopy of superheavy ($Z>100$) elements enabled determination of the nuclear moments of the heaviest nuclei, which requires high-precision atomic calculations of the relevant hyperfine structure (HFS) constants. Here, we calculated the HFS constants and energy levels for a number of nobelium (Z=102) states using the hybrid a...

We demonstrate single-shot imaging and narrow-line cooling of individual alkaline earth atoms in optical tweezers; specifically, strontium-88 atoms trapped in $515.2~\text{nm}$ light. We achieve high-fidelity single-atom-resolved imaging by detecting photons from the broad singlet transition while cooling on the narrow intercombination line, and ex...

Questioning the presumably most basic assumptions about the structure of space and time has revolutionized our understanding of Nature. State-of-the-art atomic clocks make it possible to precisely test fundamental symmetry properties of spacetime, and search for physics beyond the standard model at low energy scales of just a few electron volts. He...

Singly ionized lutetium has a number of fortuitous properties well suited for a design of an optical clock and corresponding applications. In this work, we study Lu+ properties relevant to a development of the clock using the relativistic high-precision method combining configuration interaction and the linearized coupled-cluster approaches. The sy...

The isotope $^{229}$Th is unique in that it possesses an isomeric state of only a few eV above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear properties of both states have to be determined precisely...

Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on u...

The singly-ionized lutetium has a number of fortuitous properties well suited for a design of an optical clock and corresponding applications. In this work, we study Lu+ properties relevant to a development of the clock using the relativistic high-precision method combining configuration interaction and the linearized coupled-cluster approaches. Th...

We propose a new frequency standard based on a 4f146s6p P03−4f136s25d(J=2) transition in neutral Yb. This transition has a potential for high stability and accuracy and the advantage of the highest sensitivity among atomic clocks to variation of the fine-structure constant α. We find its dimensionless α-variation enhancement factor to be K=−15, in...

We describe a broadly applicable experimental proposal to search for the violation of local Lorentz invariance (LLI) with atomic systems. The new scheme uses dynamic decoupling and can be implemented in current atomic clock experiments, with both single ions and arrays of neutral atoms. Moreover, the scheme can be performed on systems with no optic...

We propose a new frequency standard based on a $4f^{14} 6s6p~ ^3\!P_0 - 4f^{13} 6s^2 5d ~(J=2)$ transition in neutral Yb. This transition has a potential for high stability and accuracy and the advantage of the highest sensitivity among atomic clocks to variation of the fine-structure constant $\alpha$. We find its dimensionless $\alpha$-variation...

We describe a broadly applicable experimental proposal to search for the violation of local Lorentz invariance (LLI) with atomic systems. The new scheme uses dynamic decoupling and can be implemented in current atomic clocks experiments, both with single ions and arrays of neutral atoms. Moreover, the scheme can be performed on systems with no opti...

We address the problem of the lattice Stark shifts in the Sr clock caused by the multipolar $M1$ and $E2$ atom-field interactions and by the term nonlinear in lattice intensity and determined by the hyperpolarizability. We have developed an approach to calculate hyperpolarizabilities for atoms and ions based on a solution of the inhomogeneous equat...

Energy levels, wavelengths, magnetic-dipole and electric-quadrupole transition rates between the low-lying states are evaluated for W51+ to W54+ ions with 3d
n
(n = 2 to 5) electronic configurations by using an approach combining configuration interaction with the linearized coupled-cluster single-double method. The QED corrections are directly inc...

We calculate the g factor of the 6s6pP03 state of 199 and 201 mercury isotopes using a relativistic high-precision all-order method that combines the configuration interaction and the coupled-cluster approaches. Our values g(Hg199)=−0.9485(49)×10−3 and g(Hg201)=0.3504(18)×10−3 are in agreement with the experimental measurements within the 0.5% theo...

We calculate the $g$-factor of the $6s6p~ ^3\!P_0$ state of 199 and 201 mercury isotopes using a relativistic high-precision all-order method that combines the configuration interaction and the coupled-cluster approaches. Our values $g(^{199}{\rm Hg}) = -0.9485(49) \times 10^{-3}$ and $g(^{201}{\rm Hg}) = -0.3504(18) \times 10^{-3}$ are in agreemen...

We study effective three-particle interactions between valence electrons, which are induced by the core polarization. Such interactions are enhanced when valence orbitals have strong overlap with the outermost core shell, in particular for the systems with partially filled f-shell. We find that in certain cases the three-particle contributions are...

Three particle forces are known to be very important in nuclear physics. In atoms such forces appear between valence electrons in the second order of many-body perturbation theory due to the exchange interaction with the core. Usually their contribution to the valence energy is very small, of the order of few inverse centimeters. However, for atoms...

Singly ionised Lutetium has recently been suggested as a potential clock candidate. Here we report a joint experimental and theoretical investigation of \ce{Lu^+}. Measurements relevant to practical clock operation are made and compared to atomic structure calculations. Calculations of scalar and tensor polarizabilities for clock states over a rang...

We optically excite the electronic state 3s3p P03 in Mg24 atoms, laser cooled and trapped in a magic-wavelength lattice. An applied magnetic field enhances the coupling of the light to the otherwise strictly forbidden transition. We determine the magic wavelength, the quadratic magnetic Zeeman shift, and the transition frequency to be 468.46(21) nm...

We have further developed and extended a method for calculation of atomic
properties based on a combination of the configuration interaction and
coupled-cluster approach. We have applied this approach to the calculation of
different properties of atomic lead, including the energy levels, hyperfine
structure constants, electric-dipole transition amp...

We have measured the hyperfine structure and isotope shifts of the 402.0- and 399.6-nm resonance lines in Th+229. These transitions could provide pathways towards the excitation of the Th229 low-energy isomeric nuclear state. An unexpected negative isotope shift relative to Th+232 is observed for the 399.6-nm line, indicating a strong Coulomb coupl...

In many applications a source of the black-body radiation (BBR) can be highly
anisotropic. This leads to the BBR shift that depends on tensor polarizability
and on the projection of the total angular momentum of ions and atoms in a
trap. We derived formula for the anisotropic BBR shift and performed numerical
calculations of this effect for Ca$^+$...

We optically excite the electronic state $3s3p~^3P_{0}$ in $^{24}$Mg atoms,
laser-cooled and trapped in a magic-wavelength lattice. An applied magnetic
field enhances the coupling of the light to the otherwise strictly forbidden
transition. We determine the magic wavelength, the quadratic magnetic Zeeman
shift and the transition frequency to be 468...

Lorentz symmetry is one of the cornerstones of modern physics. However, a
number of theories aiming at unifying gravity with the other fundamental
interactions including string field theory suggest violation of Lorentz
symmetry [1-4].
While the energy scale of such strongly Lorentz symmetry-violating physics is
much higher than that currently attai...

We have measured the hyperfine structure and isotope shifts of the 402.0 nm
and 399.6 nm resonance lines in 229Th+. These transitions could provide
pathways towards the 229Th isomeric nuclear state excitation. An unexpected
negative isotope shift relative to 232Th+ is observed for the 399.6 nm line,
indicating a strong Coulomb coupling of the excit...