Collisional and radiative effects in the state-selective preparation of translationally cold molecular ions in ion traps

Tong, Xin; Wild, Dieter; Willitsch, Stefan

doi:10.1103/physreva.83.023415

Cited by 38 publications

(69 citation statements)

References 60 publications

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“…For photoionization, a two-color [2+1'] resonance-enhanced multiphoton ionization (REMPI) scheme was employed. [12,13] By setting the energy of the third photon just above the lowest ionization threshold of N 2 , the N 2 + ions were only produced in the X 2 nuclear spin isomers. As seen in Fig.…”

Section: Methodsmentioning

confidence: 99%

Forbidden Vibrational Transitions in Cold Molecular Ions: Experimental Observation and Potential Applications

Germann¹,

Tonga

Willitsch

2015

Chimia

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A range of interesting fundamental scientific questions can be addressed by high-precision molecular spectroscopy. A promising way towards this goal is the measurement of dipole-forbidden vibrational transitions in molecular ions. We have recently reported the first such observation in a molecular ion. [1] Here, we give an overview of our method and our results as well as an outlook on potential future applications.

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Section: Methodsmentioning

confidence: 99%

Forbidden Vibrational Transitions in Cold Molecular Ions: Experimental Observation and Potential Applications

Germann¹,

Tonga

Willitsch

2015

Chimia

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“…Our experimental set-up has been described in detail previously 19,20 . It consists of a linear RF ion trap operating at a RF amplitude V RF,0−p = 120 V and a RF frequency Ω RF = 2π × 3.2 MHz.…”

Section: Methodsmentioning

confidence: 99%

“…3). The lifetime of the N + = 0 level of the state-selected N 2 + ions was determined to be ≈15 min under our experimental conditions 19 , limited by collisions with residual background gas molecules 20 .…”

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confidence: 99%

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confidence: 99%

“…Our approach capitalizes on the very long interrogation times (up to several minutes) enabled by the sympathetic cooling and subsequent spatial localization of individual N 2 + ions in a Coulomb crystal 10 . The sensitivity of the measurement is enhanced by confining the population of the molecules to a single rotational quantum state and using a highly sensitive charge-transfer (CT) reaction scheme for the detection of absorption events 19,20 .In our experiments, we focused on the observation of specific hyperfine components of the S(0) line of the IR fundamental excitation of N 2 + -that is, the transition from the vibrational and rotational ground state (v + = 0, N + = 0) to the second rotationally excited level (N + = 2) of the first vibrationally excited state (v + = 1) within the electronic ground state. Here, v + and N + denote the vibrational and rotational quantum numbers of the ion, and and refer to the lower and upper level of the transition, respectively.…”

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Observation of electric-dipole-forbidden infrared transitions in cold molecular ions

2014

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Spectroscopic transitions in atoms and molecules that are not allowed within the electric-dipole approximation, but occur because of higher-order terms in the interaction between matter and radiation, are termed dipole-forbidden 1 . These transitions are extremely weak and therefore exhibit very small natural linewidths. Dipole-forbidden optical transitions in atoms form the basis of next-generation atomic clocks 2,3 and of high-fidelity qubits used in quantum information processors and quantum simulators 4 . In molecules, however, such transitions are much less characterized, reflecting the considerable challenges to address them. Here, we report direct observation of dipole-forbidden, electric-quadrupole-allowed infrared (IR) transitions in a molecular ion. Their detection was enabled by the very long interrogation times of several minutes a orded by the sympathetic cooling of individual quantum-state-selected molecular ions into the nearly perturbation-free environment of a Coulomb crystal. The present work paves the way for new mid-IR frequency standards and precision spectroscopic measurements on single molecules in the IR domain 5 .Recent technological advances in the cooling and manipulation of molecules have opened up perspectives for new types of precision measurements. Fundamental questions, such as a possible time variation of fundamental physical constants 6 , the magnitude of the dipole moment of the electron 7 , the existence of additional fundamental interactions 8 and the effects of parity-violating interactions in chiral molecules 9 , can now be addressed by molecular spectroscopy at an unprecedented precision.Systems suited for precise spectroscopic measurements need to exhibit narrow spectral lines. Experiments need to allow for long interrogation times to minimize line broadening induced by the finite measurement time. Moreover, studies should be performed in a well-controlled and isolated environment. Trapped cold ions spatially localized in a Coulomb crystal 10 with sufficiently strong confinement to allow Doppler-free excitation in the Lamb-Dicke regime fulfil these requirements. Together with ultracold atoms in optical lattices 3 , they represent one of the most advanced systems used in state-of-the-art precision spectroscopic measurements. Indeed, many of the currently most precise spectroscopic experiments rely on dipole-forbidden electronic transitions in Coulomb-crystallized atomic ions 2,11 . By contrast, to the best of our knowledge no dipole-forbidden vibrational-that is, IR-spectra of molecular ions have been reported so far. Studies of vibrational transitions in molecules, however, are attractive as they probe different spectral domains and dynamic regimes from those in studies of atomic systems 5,8,12 .Dipole-forbidden vibrational transitions in molecules 13 are several orders of magnitude weaker than dipole-forbidden optical transitions typically used in atoms 2,3 , rendering their observation challenging. Thus far, they were observed only in a handful of neutral diatomics, suc...

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Chemistry With Controlled Ions

Willitsch

2017

Advances in Chemical Physics

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Collisional and radiative effects in the state-selective preparation of translationally cold molecular ions in ion traps

Cited by 38 publications

References 60 publications

Forbidden Vibrational Transitions in Cold Molecular Ions: Experimental Observation and Potential Applications

Forbidden Vibrational Transitions in Cold Molecular Ions: Experimental Observation and Potential Applications

Observation of electric-dipole-forbidden infrared transitions in cold molecular ions

Chemistry With Controlled Ions

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