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Towards Collinear Laser Spectroscopy of Radioactive Molecules Utilizing In-trap Produced Molecular Ion Beam

W. C. Mei, S. J. Chen, X. F. Yang, J. H. Lv, D. Y. Chen, H. R. Hu, Y. F. Guo, Z. Yan, Y. P. Jing, C. Zhang, Y. P. Lin, T. X. Gao, X. Shen, S. W. Bai, R. F. Garcia Ruiz, J. Yang, Y. L. Ye

Abstract

Molecules containing short-lived isotopes, namely radioactive molecules, are among the most promising candidates for probing new physics beyond the Standard Model, although their production and spectroscopic measurements remain technically challenging. Here, we demonstrate an integrated methodology that combines formation of molecular ion beams in a radiofrequency quadrupole cooler-buncher with collinear laser spectroscopy. As a proof-of-principle experiment, we successfully produce molecular ions such as $\rm BaF^+$ and $\rm YbF^+$ via in-trap ion-molecule reactions and perform high-resolution laser spectroscopy of the target molecule $\rm ^{138}BaF$. Vibrational and rotational structures of $\rm ^{138}BaF$ across different electronic states are obtained using resonance-enhanced multiphoton ionization schemes, confirming the feasibility of the proposed methodology. This work establishes a practical route for future formation and spectroscopic studies of short-lived radioactive molecules, such as those containing $\rm ^{225}Ra$, at radioactive ion beam facilities.

Towards Collinear Laser Spectroscopy of Radioactive Molecules Utilizing In-trap Produced Molecular Ion Beam

Abstract

Molecules containing short-lived isotopes, namely radioactive molecules, are among the most promising candidates for probing new physics beyond the Standard Model, although their production and spectroscopic measurements remain technically challenging. Here, we demonstrate an integrated methodology that combines formation of molecular ion beams in a radiofrequency quadrupole cooler-buncher with collinear laser spectroscopy. As a proof-of-principle experiment, we successfully produce molecular ions such as and via in-trap ion-molecule reactions and perform high-resolution laser spectroscopy of the target molecule . Vibrational and rotational structures of across different electronic states are obtained using resonance-enhanced multiphoton ionization schemes, confirming the feasibility of the proposed methodology. This work establishes a practical route for future formation and spectroscopic studies of short-lived radioactive molecules, such as those containing , at radioactive ion beam facilities.
Paper Structure (7 sections, 6 equations, 6 figures, 3 tables)

This paper contains 7 sections, 6 equations, 6 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Experimental Setup
  3. In-trap Molecular Production
  4. Collinear Resonance Ionization Spectroscopy of In-trap Produced Molecules
  5. Vibrational Structure of $\mathrm{^{138}BaF}$ molecules
  6. Rotational Structure of $\mathrm{^{138}BaF}$ molecules
  7. Summary and Outlook

Figures (6)

  • Figure 1: Schematic of the offline PLASEN setup and their electrostatic components. The main systems required for performing collinear laser spectroscopy of molecules are highlithed: (a) molecular production in RFQ-CB; (b) neutralization of molecular ions in CEC; (c) REMPI of molecules in IR.
  • Figure 2: Mass spectra of the molecular products and remaining unreacted reactants from ion-molecule reactions in the RFQ-CB: (a) $\mathrm{Ba^{+}+CF_4}$; (b) $\mathrm{Yb^{+}+CF_4}$
  • Figure 3: Time of flight (TOF) spectra of the molecular products and residual reactants from ion-molecule reactions in the RFQ-CB: (a) $\mathrm{Ba^{+}+CF_4}$; (b) $\mathrm{Yb^{+}+CF_4}$
  • Figure 4: Relative amount of formed molecular ions $\mathrm{BaF^{+}}$ created in the RFQ-CB and the residual amount of reactants $\mathrm{Ba^{+}}$ as a function of the flow rate used for $\mathrm{CF_{4}}$. The relative amount of $\mathrm{Ba^{+}}$ and $\mathrm{BaF^{+}}$ indicated on the y-axis are normalized to their respective maximum values and are given in arbitrary units (a.u.).
  • Figure 5: Vibronic spectrum of $\mathrm{D~^{2}\Sigma^{+}\leftarrow X~^{2}\Sigma^{+}}$ transition in $\mathrm{^{138}BaF}$ through (1+1)-REMPI scheme (inset).
  • ...and 1 more figures