arXiv subjects

R. W. Field

Publications and source records attributed to R. W. Field.

6 recordsLinked to original sources

arXiv2024

Ionization potential of radium monofluoride

The ionization potential (IP) of radium monofluoride (RaF) was measured to be 4.969(2)[10] eV, revealing a relativistic enhancement in the series of alkaline earth monofluorides. The results are in agreement with a relativistic coupled-cluster prediction of 4.969[7] eV, incorporating up to quantum electrodynamics corrections. Using the same computational methodology, an improved calculation for the dissociation energy ($D_{0}$) of 5.54[5] eV is presented. This confirms that radium monofluoride joins the small group of diatomic molecules for which $D_{0}>\mathrm{IP}$, paving the way for precision control and interrogation of its Rydberg states.

physics.atom-ph↗

arXiv2023

Pinning down electron correlations in RaF via spectroscopy of excited states and high-accuracy relativistic quantum chemistry

We report the spectroscopy of the 14 lowest excited electronic states in the radioactive molecule radium monofluoride (RaF). The observed excitation energies are compared with fully relativistic state-of-the-art Fock-space coupled cluster (FS-RCC) calculations, which achieve an agreement of >=99.64% (within ~12 meV) with experiment for all states. Guided by theory, a firm assignment of the angular momentum and term symbol is made for 10 states and a tentative assignment for 4 states. The role of high-order electron correlation and quantum electrodynamics effects in the excitation energy of excited states is studied, found to be important for all states. Establishing the simultaneous accuracy and precision of calculations is an important step for research at the intersection of particle, nuclear, and chemical physics, including searches of physics beyond the Standard Model, for which RaF is a promising probe.

physics.atom-ph↗

arXiv2022

Fourier-transform spectroscopy of $^{13}$C$^{17}$O and deperturbation analysis of the A$^1Π$ ($ν$ = 0 - 3) levels

The high-resolution B$^1Σ^+$ - A$^1Π$ (0, 0) and (0, 3) emission bands of the less-abundant $^{13}$C$^{17}$O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm$^{-1}$. These spectra are combined with high-resolution photoabsorption measurements of the $^{13}$C$^{17}$O B$^1Σ^+$ $\leftarrow$ X$^1Σ^+$ (0, 0), B$^1Σ^+$ $\leftarrow$ X$^1Σ^+$ (1, 0) and C$^1Σ^+$ $\leftarrow$ X$^1Σ^+$ (0, 0) bands recorded with an accuracy of 0.01 cm$^{-1}$ using the vacuum ultraviolet Fourier-transform spectrometer, installed on the DESIRS beamline at the SOLEIL synchrotron. In the studied 17,950 - 22,500 cm$^{-1}$ and 86,800 - 92,100 cm$^{-1}$ regions, 480 transitions have been measured. These new experimental data were combined with data from the C $\to$ A and B $\to$ A systems, previously analyzed in 13C17O. The frequencies of 1003 transitions derived from 12 bands were used to analyze the perturbations between the A$^1Π$ ($ν$ = 0 - 3) levels and rovibrational levels of the d$^3Δ_i$, e$^3Σ^-$, a$'{}^3Σ^+$, I$^1Σ^-$ and D$^1Δ$ states as well as to a preliminary investigation of weak irregularities that appear in the B$^1Σ^+$ ($ν$ = 0) level. Deperturbed molecular constants and term values of the A$^1Π$ state were obtained. The spin-orbit and L-uncoupling interaction parameters as well as isotopologue-independent spin-orbit and rotation-electronic perturbation parameters were derived.

physics.chem-ph↗

arXiv2018

Precision spectroscopy and comprehensive analysis of perturbations in the $A\,{}^1Π(v=0$) state of ${}^{\rm 13}$C${}^{\rm 18}$O

We have reinvestigated the A$^1Π$$(v=0)$ level of $^{13}$C$^{18}$O\ using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A$^1Π-\textrm{X}^1Σ^+$$(0, 0)$, e$^3Σ^--\textrm{X}^1Σ^+$$(1, 0)$, d$^3Δ-\textrm{X}^1Σ^+$$(4, 0)$, a$'^3Σ^+-\textrm{X}^1Σ^+$$(9, 0)$, and \atX$(11, 0)$ bands. In addition, Fourier-transform emission spectroscopy in the visible range is performed on the ${\rm B}^1Σ^+-{\rm A}^1Π$$(0, 0)$ band. Spectra of the \BX$(0, 0)$ band are measured in order to tie information from the latter emission data to the level structure of A$^1Π$$(v=0)$. The high pressures in the absorption cell at the synchrotron and the high temperatures in the emission discharge permitted monitoring of high rotational quantum levels in A$^1Π$$(v=0)$ up to $J=43$. All information, in total over 900 spectral lines, was included in an effective-Hamiltonian analysis of the A$^1Π(v=0, J)$ levels that are directly perturbed by the e$\,^3Σ^-$$(v=1)$, d$^3\!Δ$$(v=4)$, a$'^3Σ^+$$(v=9)$, d$^3\!Δ$$(v=0)$, I$\,^1Σ^-$$(v=0, 1)$ close-lying levels and the e$\,^3Σ^-$$(v=0,2)$, d$^3\!Δ$$(v=3,5)$, a$'^3Σ^+$$(v=8,10)$ remote levels, as well being indirectly influenced by the a$^3Π$$(v=10, 11)$ state. The influence of nine further perturber levels and their interactions was investigated and are not significant for reproducing the present experimental data. This analysis leads to a much improved description in terms of molecular constants and interaction parameters, compared to previous studies of the same energy region for other CO isotopologues.

physics.atom-ph↗

arXiv2016

The rotation-vibration structure of the SO$_2$ $\mathrm{\tilde{C}}^1\mathrm{B}_2$ state explained by a new internal coordinate force field

A new quartic force field for the SO$_2$ $\tilde{\text{C}}$$^1$B$_2$ state has been derived, based on high resolution data from S$^{16}$O$_2$ and S$^{18}$O$_2$. Included are eight $b_2$ symmetry vibrational levels of S$^{16}$O$_2$ reported in the first paper of this series [G. B. Park, $\textit{et al.}$, J. Chem. Phys. $\textbf{144}$, 144311 (2016)]. Many of the experimental observables not included in the fit, such as the Franck-Condon intensities and the Coriolis-perturbed effective $C$ rotational constants of highly anharmonic $\tilde{\text{C}}$ state vibrational levels, are well reproduced using our force field. Because the two stretching modes of the $\tilde{\text{C}}$ state are strongly coupled via Fermi-133 interaction, the vibrational structure of the $\tilde{\text{C}}$ state is analyzed in a Fermi-system basis set, constructed explicitly in this work via $\textit{partial}$ $\textit{diagonalization}$ of the vibrational Hamiltonian. The physical significance of the Fermi-system basis is discussed in terms of semiclassical dynamics, based on study of Fermi-resonance systems by Kellman and coworkers [M. E. Kellman and L. Xiao, J. Chem. Phys. $\textbf{93}$, 5821 (1990)]. By diagonalizing the vibrational Hamiltonian in the Fermi-system basis, the vibrational characters of all vibrational levels can be determined unambiguously. It is shown that the bending mode cannot be treated separately from the coupled stretching modes, particularly at vibrational energies of more than 2000 cm$^{-1}$. Based on our force field, the structure of the Coriolis interactions in the $\tilde{\text{C}}$ state of SO$_2$ is also discussed. We identify the origin of the alternating patterns in the effective $C$ rotational constants of levels in the vibrational progressions of the symmetry-breaking mode, $ν_β$ (which correlates with the antisymmetric stretching mode in our assignment scheme).

physics.chem-ph↗

arXiv2015

Spectroscopy and perturbation analysis of the CO A$^1Π-$X$^1Σ^+$ (2,0), (3,0) and (4,0) bands

The (2,0) (3,0) and (4,0) bands of the A$^1Π-$X$^1Σ^+$ system of $^{12}$C$^{16}$O have been re-investigated by high-resolution vacuum ultraviolet absorption spectroscopy. A VUV Fourier-transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet-cooled spectrum, a room temperature static gas spectrum and a high temperature (900 K) quasi-static gas spectrum, resulting in absolute accuracies of 0.01$-$0.02 cm$^{-1}$ for the rotational line frequencies. Precise laser-based data were included in the analysis allowing for a highly accurate determination of band origins. Rotational levels up to $J=52$ were observed. The data were used to perform an improved analysis of the perturbations in the A$^1Π$, $v=2$, $v=3$, and $v=4$ levels by vibrational levels of the D$^1Δ$, I$^1Σ^-$, e$^3Σ^-$, d$^3Δ$, and a$'^3Σ^+$ states.

physics.atom-ph↗