The Zero-Quantum-Defect Method and the Fundamental Vibrational Interval of H2+_2^+

The fundamental vibrational interval of H$_{2}^+$ has been determined to be $\Delta G _{1/2} = 2191.126\,614(17)$ cm$^{-1}$ by continuous-wave laser spectroscopy of Stark manifolds of Rydberg states of H$_2$ with the H$_{2}^+$ ion core in the ground and first vibrationally excited states. Extrapolation of the Stark shifts to zero field yields the zero-quantum-defect positions $-R_{\textrm{H}_2}$/$n^2$, from which ionization energies can be determined. Our new result represents a four-order-of-magnitude improvement compared to earlier measurements. It agrees, within the experimental uncertainty, with the value of 2191.126\,626\,344(17)(100) cm$^{-1}$ determined in non-relativistic quantum electrodynamic calculations V. Korobov, L. Hilico and J.-Ph. Karr, Phys. Rev. Lett. 118, 233001 (2017) http://doi.org/10.1103/PhysRevLett.118.233001

Benchmarking theory with an improved measurement of the ionization and dissociation energies of H2_2

The dissociation energy of H$_2$ represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF $^1\Sigma_g^+(v=0,N=1)$ state and the 54p1$_1$ Rydberg state of H$_2$. When combined with previously determined intervals, this new measurement leads to an improved value of the dissociation energy $D_0^{N=1}$ of ortho-H$_2$ that has, for the first time, reached a level of uncertainty that is three times smaller than the contribution of about 1 MHz resulting from the finite size of the proton. The new result of 35999.582834(11) cm$^{-1}$ is in remarkable agreement with the theoretical result of 35999.582820(26) cm$^{-1}$ obtained in calculations including high-order relativistic and quantum electrodynamics corrections, as reported in the companion article (M. Puchalski, J. Komasa, P. Czachorowski and K. Pachucki, submitted). This agreement resolves a recent discrepancy between experiment and theory that had hindered a possible use of the dissociation energy of H$_2$ in the context of the current controversy on the charge radius of the proton

Phase protection of Fano-Feshbach resonances

Decay of bound states due to coupling with free particle states is a general phenomenon occurring at energy scales from MeV in nuclear physics to peV in ultracold atomic gases. Such a coupling gives rise to Fano-Feshbach resonances (FFR) that have become key to understanding and controlling interactions—in ultracold atomic gases, but also between quasiparticles, such as microcavity polaritons. Their energy positions were shown to follow quantum chaotic statistics. In contrast, their lifetimes have so far escaped a similarly comprehensive understanding. Here, we show that bound states, despite being resonantly coupled to a scattering state, become protected from decay whenever the relative phase is a multiple of π. We observe this phenomenon by measuring lifetimes spanning four orders of magnitude for FFR of spin–orbit excited molecular ions with merged beam and electrostatic trap experiments. Our results provide a blueprint for identifying naturally long-lived states in a decaying quantum system

Nonadiabatic effects on the positions and lifetimes of the low-lying rovibrational levels of the GK 1Σ+g and H 1Σ+g states of H2

ISSN:1463-9084ISSN:1463-907

Precision millimetre-wave spectroscopy and calculation of the Stark manifolds in high Rydberg states of para-H2_2

Precision measurements of transitions between singlet ($S=0$) Rydberg states of H$_2$ belonging to series converging on the \mathrm{X}^+\,^2\Sigma_g^+(v^+=0,N^+=0) state of H$_2^+$ have been carried out by millimetre-wave spectroscopy under field-free conditions and in the presence of weak static electric fields. The Stark effect mixes states with different values of the orbital-angular-momentum quantum number $\ell$ and leads to quadratic Stark shifts of low-$\ell$ states and to linear Stark shifts of the nearly degenerate manifold of high-$\ell$ states. Transitions to the Stark manifold were observed for the principal numbers 50 and 70, at fields below 50 mV/cm, with linewidths below 500~kHz. The energy-level structure was calculated using a matrix-diagonalisation approach, in which the zero-field positions of the $\ell\leq 3$ Rydberg states were obtained either from multichannel-quantum-defect-theory calculations or experiment, and those of the $\ell\geq 4$ Rydberg states from a long-range core-polarisation model. This approach offers the advantage of including rovibronic channel interactions through the MQDT treatment while retaining the advantages of a spherical basis for the determination of the off-diagonal elements of the Stark operator. Comparison of experimental and calculated transition frequencies enabled the quantitative description of the Stark manifolds, with residuals typically below 50 kHz. We demonstrate how the procedure leads to quantum defects and binding energies of high Rydberg states with unprecedented accuracy, opening up new prospects for the determination of ionisation energies in molecules.Comment: 18 pages, 12 figure

Metrology of high- n Rydberg states of molecular hydrogen with Δν/ν=2×10-10 accuracy

ISSN:1094-1622ISSN:0556-2791ISSN:1050-294

Improved ionization and dissociation energies of the deuterium molecule

The ionization energy of D2 has been determined experimentally from measurements involving two-photon Doppler-free vacuum-ultraviolet pulsed laser excitation and near-infrared continuous-wave laser excitation to yield EI(D2)=124745.393739(26) cm-1. From this value, the dissociation energy of D2 is deduced to be D0(D2)=36748.362282(26) cm-1, representing a 25-fold improvement over previous values, and it was found to be in good agreement (at 1.6s) with recent ab initio calculations of the four-particle nonadiabatic relativistic energy and of quantum-electrodynamic corrections up to order ma6. This result constitutes a test of quantum electrodynamics in the molecular domain, while a perspective is opened to determine nuclear charge radii from molecules.ISSN:1094-1622ISSN:0556-2791ISSN:1050-294

Ionization and dissociation energies of HD and dipole-induced

ISSN:1094-1622ISSN:0556-2791ISSN:1050-294