Electric-field dissociation of weakly bound molecular ions

Letter
Open Access

Electric-field dissociation of weakly bound molecular ions

Jesús Pérez-Ríos

Phys. Rev. A 104, L031302 – Published 13 September 2021

Abstract

We present a study on the dissociation of a weakly bound molecular ion in the presence of an external time-dependent electric field based on a full quantum treatment of the dynamics. We focus on the dissociation dynamics of a molecular ion in a Paul trap relevant for atom-ion hybrid traps. Our results show that a weakly bound molecular ion survives in a Paul trap giving a theoretical ground to previous experimental findings [A. Krükow et al. Phys. Rev. Lett. 116, 193201 (2016) and A. Mohammadi et al., Phys. Rev. Research 3, 013196 (2021)]. In particular, we find that weakly bound molecular ions are more likely to survive in traps with a large rf frequency. Similarly, we show that applying an electric field ramp is an efficient method to state-selectively detect weakly bound molecular ions, analogous to the well-known selective field ionization technique applied in Rydberg atoms.

Received 18 May 2021
Revised 30 August 2021
Accepted 31 August 2021

DOI:https://doi.org/10.1103/PhysRevA.104.L031302

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Chemical reactions Light-matter interaction

Ions Trapped ions

Atomic, Molecular & Optical

Authors & Affiliations

Jesús Pérez-Ríos

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany and Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands

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Issue

Vol. 104, Iss. 3 — September 2021

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Images

Figure 1
Rovibrational energy spectrum of the ${}^{174}{Yb} {}^{87}{Rb}^{+}$ molecular ion as a function of the time-independent electric field strength $F$ . The dashed lines correspond to a few of the relevant rovibrational states labeled by the vibrational quantum number $v$ and the rotational quantum number $j$ . Lines with the same colors represent rotational states of the same vibrational state: the green lines refer to the $v = - 4$ , the gray line to the $v = - 5$ , whereas the black lines refer to deeply bound vibrational states of the molecular ion. The shaded region represents the onset of dissociation. Please note that the states above $E = 0$ represent high level rotational states as a consequence of how the rovibrational energy is obtained: $E_{v j} = E_{v} + B_{v} j (j + 1)$ . The left panel displays schematically the nature of the molecular ion at different electric field strengths; the lower panel represents a weakly bound molecular ion, whereas the upper panel stands for a dissociated molecular ion.
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Figure 2
Molecular ion energy of the $(v = - 1; j = 0)$ state of ${}^{174}{Yb} {}^{87}{Rb}^{+}$ as a function of time for different electric field pulses. Panel (a) is for a Gaussian pulse centered at $t_{0} = \frac{T_{rot}}{2} = \frac{π}{2 B_{- 1}}$ with $τ = 500 ns$ and $F_{0} = 0.001 68 V / cm$ , whereas panel (b) refers to rf-type electric field with $ω_{rf} = 2 π \times 2 MHz$ , $F_{dc} = 0.001 V / cm$ , and $F_{ac} = 0.001 56 V / cm$ . The color code refers to the probability of populating rovibrational states with $v < - 1$ , i.e., the vibrational quenching probability.
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Figure 3
Dissociation field strength for different vibrational states of ${}^{174}{Yb} {}^{87}{Rb}^{+}$ and ${}^{174}{Yb} {}^{6}{Li}^{+}$ assuming Gaussian pulse with $τ = 100 ns$ . The inset shows the electric field dissociation for $v = - 1$ states as a function of the pulse duration $τ$ . The dashed lines correspond to a fitting of the data as explained in the text, whereas the vertical lines represent the rotational period of the involved vibrational states accordingly with the color code employed in the main figure.
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Figure 4
Phase diagram for the dissociation of a weakly bound molecular ion. The phase diagram presents the region of the parameter space for which a given ac electric field $F_{ac}$ dissociates the molecular ion for a given $ω_{rf}$ assuming a fixed dc field value of 0.001 V/cm. Panel (a) refers to the $| v = - 1, j = 0 〉$ state for ${}^{174}{Yb} {}^{87}{Rb}^{+}$ . Panel (b) is for the $| v = - 2, j = 0 〉$ state of ${}^{138}{Ba} {}^{87}{Rb}^{+}$ , whereas panel (c) is for the $| v = - 1, j = 0 〉$ state of ${}^{174}{Yb} {}^{6}{Li}^{+}$ . In panel (d) a different phase diagram is presented for the $| v = - 1, j = 0 〉$ state of ${}^{174}{Yb} {}^{6}{Li}^{+}$ , in which the ac electric field values capable to dissociate the molecular ion are shown as a function of the ac electric field for $ω_{rf} = 2 π \times 2 MHz$ .
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