We report a direct measurement of the 0-1 R(0) vibrational transition frequency in ground-state hydrogen deuteride (HD) using infrared-ultraviolet double resonance spectroscopy in a molecular beam. Ground-state molecules are vibrationally excited using a frequency comb referenced continuous-wave infrared laser, and the excited molecules are detected via state-selective ionization with a pulsed ultraviolet laser. We determine an absolute transition frequency of 111 448 815 477(13) kHz. The 0.12 parts-per-billion (ppb) uncertainty is limited primarily by the residual first-order Doppler shift.
Spectroscopy of the Hyperfine Structure of HD$^+$ in Rotationally Excited States with 10-ppb Uncertainty
ASML；Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France（卡斯勒-布罗塞尔实验室，索邦大学，法国国家科学研究中心，巴黎文理研究大学，法兰西学院）；LaserLaB, Department of Physics and Astronomy, Vrije Universiteit Amsterdam（激光实验室，阿姆斯特丹自由大学物理与天文系）；Science Institute and Faculty of Physical Sciences, University of Iceland（冰岛大学理学院和物理科学学院）
We report the creation of a sample of over 1000 ultracold $^{87}$RbCs molecules in the lowest rovibrational ground state, from an atomic mixture of $^{87}$Rb and Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be $h c \times 3811.576(1)$ cm$^{-1}$ and the $|v''=0, J''=0>$ to $|v''=0, J''=2>$ splitting to be $h \times 2940.09(6)$ MHz. Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses a…
We propose and experimentally investigate a scheme for narrow-line cooling of KRb molecules in the rovibrational ground state. We show that the spin-forbidden $\mathrm{X^1Σ^+} \rightarrow \mathrm{b^3Π_{0^+}}$ transition of KRb is ideal for realizing narrow-line laser cooling of molecules because it has highly diagonal Franck-Condon factors and narrow linewidth. In order to confirm the prediction, we performed the optical and microwave spectroscopy of ultracold $^{41}$K$^{87}$Rb molecules, and determined the linewidth ($2π\times$ 4.9(4) kHz) and Franck-Condon factors for the $\mathrm{X^1Σ^+} (v…
Astrophysical modeling of processes in environments that are not in local thermal equilibrium requires the knowledge of state-to-state rate coefficients of rovibrational transitions in molecular collisions. These rate coefficients can be obtained from coupled-channel (CC) quantum scattering calculations which are very demanding, however. Here we present various approximate, but more efficient methods based on the coupled-states approximation (CSA) which neglects the off-diagonal Coriolis coupling in the scattering Hamiltonian in body-fixed coordinates. In particular, we investigated a method c…
Precise energies of rovibrational states of the exotic hydrogen-like molecule $(dtμ)Xee$ are of importance for $dtμ$ resonant formation, which is a key process in the muon-catalyzed fusion cycle. The effect of the internal structure and motion of the $dtμ$ quasi-nucleus on energy levels is studied using the three-body description of the $(dtμ)Xee$ molecule based on the hierarchy of scales and corresponding energies of its constituent subsystems. For a number of rovibrational states of $(dtμ)dee$ and $(dtμ)tee$, the shifts and splittings of energy levels are calculated in the second order of th…
We study the feasibility of nearly-degenerate two-photon rovibrational spectroscopy in ensembles of trapped, sympathetically cooled hydrogen molecular ions using a resonance-enhanced multiphoton dissociation (REMPD) scheme. Taking advantage of quasi-coincidences in the rovibrational spectrum, the excitation lasers are tuned close to an intermediate level to resonantly enhance two-photon absorption. Realistic simulations of the REMPD signal are obtained using a four-level model that takes into account saturation effects, ion trajectories, laser frequency noise and redistribution of population b…
The saturation spectrum of the R(1) transition in the (2-0) band in HD is found to exhibit a composite line shape, involving a Lamb-dip and a Lamb-peak. We propose an explanation for such behavior based on the effects of cross-over resonances in the hyperfine substructure, which is made quantitative in a density-matrix calculation. This resolves an outstanding discrepancy on the rovibrational R(1) transition frequency, which is now determined at 217 105 181 901 (50) kHz and in agreement with current theoretical calculations.
The systematic shifts of the transition frequencies in the molecular hydrogen ions are of relevance to ultra-high-resolution radio-frequency, microwave and optical spectroscopy of these systems, performed in ion traps. We develop the ab-initio description of the interaction of the electric quadrupole moment of this class of molecules with the static electric field gradients present in ion traps. In good approximation, it is described in terms of an effective perturbation hamiltonian. An approximate treatment is then performed in the Born-Oppenheimer approximation. We give an expression of the …
We demonstrate the use of a femtosecond frequency comb to coherently drive stimulated Raman transitions between terahertz-spaced atomic energy levels. More specifically, we address the $3d~^2D_{3/2}$ and $3d~^2D_{5/2}$ fine structure levels of a single trapped $^{40}$Ca$^+$ ion and spectroscopically resolve the transition frequency to be $ν_D = 1{,}819{,}599{,}021{,}534 \pm 8$ Hz. The achieved accuracy is nearly a factor of five better than the previous best Raman spectroscopy, and is currently limited by the stability of our atomic clock reference. Furthermore, the population dynamics of freq…
Optically Derived Radio-Frequency Benchmark in Methanol: A Sub-kHz Reference for Astrophysical Tests of Fundamental Physics
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain（凝聚态与纳米科学研究所，天主教鲁汶大学）；Department of Physics and Astronomy, LaserLab, Vrije Universiteit（物理与天文学系，激光实验室，自由大学）；VSL Dutch Metrology Institute（荷兰计量研究所）；Institute of Theoretical Astrophysics, The Faculty of Mathematics and Natural Sciences, University of Oslo（理论天体物理研究所，数学与自然科学学院，奥斯陆大学）；Université Paris Cité and Univ Paris Est Creteil, CNRS, LISA（巴黎西岱大学与巴黎东克雷泰伊大学，法国国家科学研究中心，LISA）
Using a free-running distributed-feedback quantum cascade laser (QCL) emitting at 9.54 $μ$m, the pressure shift parameters of four intense rovibrational transitions in the $ν_3$ fundamental band of ozone induced by oxygen (O$_2$), air and the noble gases helium (He), argon (Ar), and xenon (Xe) are obtained by employing second harmonic detection. The experimental analysis comprises a full uncertainty budget and provides line shift data which are traceable to SI. The high density of transitions in the $ν_3$ spectral region of ozone make this region particularly difficult to study with more commo…
In order to realize more sensitive eEDM measurement, it would be worthwhile to find some new laser-cooled molecules with larger internal effective electric field (E$_{eff}$), higher electric polarizability and longer lifetime of the eEDM measurement state. Here we explore the merits of mercuric monofluoride ($^{202}Hg^{19}F$, X$^ 2 Σ_{1/2}$) for its potential of laser cooling and eEDM measurement. We theoretically investigated the electronic, rovibrational and hyperfine structures and verified the highly diagonal Franck-Condon factors (FCFs) of the main transitions by the Rydberg-Klein-Rees in…
Rotational laser spectroscopy of the $X^1Σ_g^+\rightarrow B^1Π_u$ transition of $\text{Rb}_2$ molecule in a supersonic beam: As good as it gets
Instituto de Física de São Carlos, Universidade de São Paulo（圣卡洛斯物理研究所，圣保罗大学）；Université Paris-Saclay, CNRS, Laboratoire Aimé Cotton（巴黎-萨克雷大学，法国国家科学研究中心，艾梅·科唐实验室）
