QED correction for H3+_3^+

A quantum electrodynamics (QED) correction surface for the simplest polyatomic and polyelectronic system H$_3^+$ is computed using an approximate procedure. This surface is used to calculate the shifts to vibration-rotation energy levels due to QED; such shifts have a magnitude of up to 0.25 cm$^{-1}$ for vibrational levels up to 15~000 cm$^{-1}$ and are expected to have an accuracy of about 0.02 cm$^{-1}$. Combining the new H$_3^+$ QED correction surface with existing highly accurate Born-Oppenheimer (BO), relativistic and adiabatic components suggests that deviations of the resulting {\it ab initio} energy levels from observed ones are largely due to non-adiabatic effects

Learning to handle parameter perturbations in Combinatorial Optimization: An application to facility location

We present an approach to couple the resolution of Combinatorial Optimization problems with methods from Machine Learning. Specifically, our study is framed in the context where a reference discrete optimization problem is given and there exist data for many variations of such reference problem (historical or simulated) along with their optimal solution. Those variations can be originated by disruption but this is not necessarily the case. We study how one can exploit these to make predictions about an unseen new variation of the reference instance. The methodology is composed by two steps. We demonstrate how a classifier can be built from these data to determine whether the solution to the reference problem still applies to a perturbed instance. In case the reference solution is only partially applicable, we build a regressor indicating the magnitude of the expected change, and conversely how much of it can be kept for the perturbed instance. This insight, derived from a priori information, is expressed via an additional constraint in the original mathematical programming formulation. We present the methodology through an application to the classical facility location problem and we provide an empirical evaluation and discuss the benefits, drawbacks and perspectives of such an approach. Although it cannot be used in a black-box manner, i.e., it has to be adapted to the specific application at hand, we believe that the approach developed here is general and explores a new perspective on the exploitation of past experience in Combinatorial Optimization

ExoMol molecular line lists XXX: a complete high-accuracy line list for water

A new line list for H$_2$$^{16}$O is presented. This line list, which is called POKAZATEL, includes transitions between rotation-vibrational energy levels up to 41000 cm$^{-1}$ in energy and is the most complete to date. The potential energy surface (PES) used for producing the line list was obtained by fitting a high-quality ab initio PES to experimental energy levels with energies of 41000 cm$^{-1}$ and for rotational excitations up to $J=5$. The final line list comprises all energy levels up to 41000 cm$^{-1}$ and rotational angular momentum $J$ up to 72. An accurate ab initio dipole moment surface (DMS) was used for the calculation of line intensities and reproduces high-precision experimental intensity data with an accuracy close to 1 %. The final line list uses empirical energy levels whenever they are available, to ensure that line positions are reproduced as accurately as possible. The POKAZATEL line list contains over 5 billion transitions and is available from the ExoMol website (www.exomol.com) and the CDS database

High accuracy CO2_2 line intensities determined from theory and experiment

Atmospheric CO$_2$ concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5\%\ or better. Most available laboratory measurements have uncertainties much larger than this. We report a joint experimental and theoretical study providing rotation-vibration line intensities with the required accuracy. The {\it ab initio} calculations are extendible to all atmospherically important bands of CO$_2$ and to its isotologues. As such they will form the basis for detailed CO$_2$ spectroscopic line lists for future studies.Comment: 5 pages, 2 figures, 1 tabl