Speaker
Description
In the past few years, spectroscopy of radioactive molecules has been performed at ISOLDE (CERN) using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment [1]. Given their structure and chemical properties, radioactive molecules are promising candidates for studies in different fields [2], including for more efficient extraction of refractory elements from ISOLDE targets [3].
Many reference electric quadrupole moments (EQM) have been extracted from spectroscopy on stable diatomic molecules, e.g., for K, Cl, I, using KF, HCl, and HI [4,5,6]. However, given the small electric field gradient in these atomic systems or the difficulty of studying the elements in atomic form, no quadrupole moments have been measured for radioactive isotopes, using laser techniques.
Following the successful high-resolution studies of 225,226RaF [7,8], the CRIS experiment at ISOLDE performed the first hyperfine-resolved resonance ionization spectroscopy of 223RaF, revealing the quadrupole splitting of the I=3/2 223Ra isotope. The charge radii of 223,225,226Ra have been extracted from the hyperfine structure in these RaF isotopologues with a precision comparable to atomic studies [9,10]. Moreover, the hyperfine structure of 223Ra (I = 3/2) allowed the first measurement of the EQM in a short-live radioactive molecule (t1/2 = 11.4 days), exhibiting the large sensitivity of molecules to the EQM.
This contribution will focus on the retrieved nuclear moments of 223Ra from 223RaF studies and compare them with the atomic and ionic measurements found in the literature. Due to its great agreement with literature and the increased precision of the EQM in Ra isotopes, molecular laser spectroscopy could offer a new pathway towards extracting unknown quadrupole moments of radioactive isotopes using suitable molecules [11].
[1] Garcia Ruiz, R.F., et al. "Spectroscopy of short-lived radioactive molecules." Nature 581.7809 (2020): 396-400.
[2] Opportunities for Fundamental Physics Research with Radioactive Molecules, arXiv:2302.02165 (2023)
[3] Au, Mia. Production of actinide atomic and molecular ion beams at CERN-ISOLDE. No. CERN-THESIS-2023-228. 2023.
[4] Kello, Vladimir. "Determination of the quadrupole moment of the halogen nuclei (Cl, Br, I) from molecular data." Molecular Physics 89.1 (1996): 127-137.
[5] Kellö, Vladimir, and Andrzej J. Sadlej. "The quadrupole moment of the 39K and 41K nuclei from microwave data for KF and KCl." Chemical physics letters 292.4-6 (1998): 403-410.
[6] Bieroń, Jacek, et al. "Nuclear quadrupole moments of bromine and iodine from combined atomic and molecular data." Physical Review A 64.5 (2001): 052507.
[7] S. G. Wilkins et al., Observation of the distribution of nuclear magnetization in a molecule, Accepted in Science, 2025
[8] S.-M. Udrescu, et al., Precision spectroscopy and laser-cooling scheme of a radium-containing molecule”, Nature Physics (2024) online January 9, https://doi.org/10.1038/s41567-023-02296-w
[9] Wansbeek, L. W., Schlesser, S., Sahoo, B. K., Dieperink, A. E. L., Onderwater, C. J. G., & Timmermans, R. G. E. (2012). Charge radii of radium isotopes. Physical Review C—Nuclear Physics, 86(1), 015503. https://doi.org/10.1103/PhysRevC.86.015503
[10] Lynch, K. M., Wilkins, S. G., Billowes, J., Binnersley, C. L., Bissell, M. L., Chrysalidis, K., ... & Yang, X. F. (2018). Laser-spectroscopy studies of the nuclear structure of neutron-rich radium. Physical Review C, 97(2), 024309. https://doi.org/10.1103/PhysRevC.97.024309
[11] Dognon, Jean-Pierre, and Pekka Pyykkö. "Determining nuclear quadrupole moments of Bi and Sb from molecular data." Physical Chemistry Chemical Physics 25.4 (2023): 2758-2761.