arXiv : Observation of the distribution of nuclear magnetization in a molecule

Wilkins, S.G.; Wang, Q.; Flanagan, K.T.; Garcia Ruiz, R.F.; Udrescu, S.M.; Belošević, I.; Geldhof, S.; Kujanpää, S.; de Groote, R.P.; Berger, R.; Isaev, T.; Athanasakis-Kaklamanakis, M.; Franchoo, S.; Zülch, C.; Brinson, A.J.; Perrett, H.A.; Lalanne, L.; Dorne, A.; Wessolek, J.; Chrysalidis, K.; Bissell, M.L.; Au, M.; Breier, A.A.; Heinke, R.; Nichols, M.; Rothe, S.; Gaul, K.; Reilly, J.R.; Giesen, T.F.; Koszorús, Á.; Skripnikov, L.V.; Yang, X.F.; Cocolios, T.E.; Borne, B. van den; Hanstorp, D.; Neyens, G.

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Preprint
Report number	arXiv:2311.04121
Title	Observation of the distribution of nuclear magnetization in a molecule
Author(s)	Wilkins, S.G. (MIT) ; Udrescu, S.M. (MIT) ; Athanasakis-Kaklamanakis, M. (CERN ; Leuven U.) ; Garcia Ruiz, R.F. (MIT) ; Au, M. (CERN ; Mainz U.) ; Belošević, I. (TRIUMF) ; Berger, R. (Philipps U. Marburg) ; Bissell, M.L. (Manchester U.) ; Breier, A.A. (Kassel U.) ; Brinson, A.J. (MIT) ; Chrysalidis, K. (CERN) ; Cocolios, T.E. (Leuven U.) ; de Groote, R.P. (Leuven U.) ; Dorne, A. (Leuven U.) ; Flanagan, K.T. (Manchester U. ; U. Manchester (main)) ; Franchoo, S. (IJCLab, Orsay) ; Gaul, K. (Philipps U. Marburg) ; Geldhof, S. (Leuven U.) ; Giesen, T.F. (Kassel U.) ; Hanstorp, D. (U. Gothenburg (main)) ; Heinke, R. (CERN) ; Isaev, T. (CERN) ; Koszorús, Á. (CERN) ; Kujanpää, S. (Jyvaskyla U.) ; Lalanne, L. (Leuven U.) ; Neyens, G. (Leuven U.) ; Nichols, M. (U. Gothenburg (main)) ; Perrett, H.A. (Manchester U.) ; Reilly, J.R. (Manchester U.) ; Skripnikov, L.V. (CERN) ; Rothe, S. (CERN) ; Borne, B. van den (Leuven U.) ; Wang, Q. (Lanzhou U. Technol.) ; Wessolek, J. (Manchester U.) ; Yang, X.F. (Lanzhou U. Technol.) ; Zülch, C. (Philipps U. Marburg)
Imprint	2023-11-07
Subject category	physics.comp-ph ; Other Fields of Physics ; physics.chem-ph ; Chemical Physics and Chemistry ; physics.atom-ph ; Other Fields of Physics ; nucl-ex ; Nuclear Physics - Experiment
Abstract	Rapid progress in the experimental control and interrogation of molecules, combined with developments in precise calculations of their structure, are enabling new opportunities in the investigation of nuclear and particle physics phenomena. Molecules containing heavy, octupole-deformed nuclei such as radium are of particular interest for such studies, offering an enhanced sensitivity to the properties of fundamental particles and interactions. Here, we report precision laser spectroscopy measurements and theoretical calculations of the structure of the radioactive radium monofluoride molecule, $^{225}$Ra$^{19}$F. Our results allow fine details of the short-range electron-nucleus interaction to be revealed, indicating the high sensitivity of this molecule to the distribution of magnetization, currently a poorly constrained nuclear property, within the radium nucleus. These results provide a direct and stringent test of the description of the electronic wavefunction inside the nuclear volume, highlighting the suitability of these molecules to investigate subatomic phenomena.
Other source	Inspire
Copyright/License	preprint: (License: CC BY 4.0)

$\textbf{Experimental setup.} (\textbf{A}) Radium fluoride molecules are produced by impinging $1.4$-GeV protons on a high-temperature (T$=2000$~K) uranium carbide target, injected with CF$_4$ gas, then surfaced ionized and extracted using electrostatic fields (I). $^{225}$RaF is mass-selected (II) and trapped in a He-filled radiofrequency quadrupole (T~=~300~K) for up to $20$~ms (III). The bunched RaF ions are guided using electrostatic deflectors (IV), neutralized in a Na-filled charge-exchange cell (V), then overlapped with 3 pulsed lasers in a collinear geometry (VI). The resulting RaF ions are deflected and detected using an ion detector (VII). (\textbf{B}) Example of energy levels involved in a transition between hyperfine levels in an R-branch (not to scale). N, J and F correspond to the rotational, electronic and total angular momentum quantum numbers of the molecule (N and J are not good quantum numbers when $\mathrm{I} > 0$). Experimentally observed transitions are shown by upwards-pointing arrows and numbered. (\textbf{C}) Example of measured spectra showing the ion rate in arbitrary units (a.u.) as a function of the wavenumber of the first laser, Doppler corrected to the molecular rest frame and shifted by $T_{\Pi}$. The error bars show one standard deviation statistical uncertainty. Data points are connected by straight lines to guide the eye. The numbering on the individual peaks corresponds to the transitions shown in (\textbf{B}).$ $\textbf{Nuclear effects in the RaF molecule due to the Ra nucleus.} (\textbf{A}) Extracted values of the magnetic moment of $^{225}$Ra, $\mu\left(^{225}\mathrm{Ra}\right)$, in units of nuclear magnetons, $\mu_N$, assuming the Ra nucleus is a point-like magnetic dipole (left) and accounting for the distribution of the nuclear magnetization inside of the Ra nucleus (right). The difference between the two, $\mu_{BW}$($^{225}$Ra), corresponds to the effect of the distribution of the nuclear magnetization and amounts to $\sim 5\%$ of the total value of $\mu\left(^{225}\mathrm{Ra}\right)$. The black and blue error bars are the experimental and total (experimental plus theoretical) uncertainties, respectively. The center and thickness of the orange band correspond to the previously measured value and associated uncertainty of $\mu$($^{225}$Ra) in an atom \cite{arnold1987direct}. (\textbf{B}) Evolution of the calculated $A_\perp$ for increasing levels of theoretical sophistication (see main text and the Supplementary Materials for more details) \cite{skripnikov2020nuclear}. (\textbf{C}) Order-of-magnitude estimation of nuclear effects due to Ra nucleus on the energy levels of $^{223,225}$RaF. From left to right: changes in nuclear charge radius between Ra isotopes \cite{udrescu2021isotope}, point-like magnetic dipole moment, electric quadrupole moment \cite{petrov2020energy}, distribution of nuclear magnetization, anapole moment, nuclear Schiff moment \cite{flambaum2019enhanced,graner2016reduced}, magnetic quadrupole moment \cite{flambaum2022enhanced}. The electric and magnetic quadrupole moments are nonzero only for Ra isotopes with nuclear spin $\mathrm{I}>1/2$, such as $^{223}$Ra.$ $\textbf{Example of measured spectra for the $0' \leftarrow 0''$ transitions.} In the center, in blue, the fitted combined hyperfine and rovibronic spectrum of $^{225}$RaF obtained for $J\le 100$, over a range of $\sim 50$ cm$^{-1}$ is presented. Figures in magnified views show measured spectra for different regions in frequency space. The connected red dots show the experimental data, while the continuous blue lines represents the best fits to the data. The errorbars show one standard deviation statistical uncertainty. The values on the x-axis correspond to the wavenumber of the first laser used in the resonance ionization scheme, Doppler corrected to the molecular rest frame. The rate on the y-axis is given in arbitrary units (a.u.).$ Show more plots

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Record created 2023-11-22, last modified 2023-11-28

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