Communication: Visible line intensities of the triatomic hydrogen ion from experiment and theory

Abstract

Radiative charge transfer in He + + H 2 collisions in the milli-to nano-electron-volt range: A theoretical study within state-to-state and optical potential approaches

ExoMol molecular line lists – XX. A comprehensive line list for H3+

“…Nuclear motion calculations used the highly accurate global ab initio PES presented by Pavanello et al (2012b) and the related DMS given by Petrignani et al (2014). The DMS is expressed in the 7-parameter form of Lie & Frye (1992) which was found to best reproduce the observations.…”

“…For example the use of the NMT line list was instrumental in assignment and reassignment of numerous experimentally observed lines by Dinelli et al (1997). It has also been shown to be very accurate for spectroscopic intensity predictions (Pavanello et al 2012a;Petrignani et al 2014), perhaps surprisingly so. However, improved theoretical modelling of the spectroscopy of H + 3 , discussed below, implies that we are now in position to compute a line list which is both more accurate and more complete, as well as being able to rectify other known issues with the NMT list.…”

“…Theory has always played an important part in the astronomical spectroscopy of H + 3 since, as yet, there is only a single (McKellar & Watson 1998) absolute laboratory measurements of H + 3 line intensities. However, empirical tests of predicted intensities have also been provided by experiments measuring intensity ratios for transitions with widely differing wavelengths and intensities (Farnik et al 2002;Asvany et al 2007;Petrignani et al 2014). The most stringent test was provided by the visible-wavelength measurements of Petrignani et al (2014) which showed that their DMS, used here, predicted the observed intensities in a very satisfactory manner.…”

Perspective: Accurate ro-vibrational calculations on small molecules

“…Here a more pragmatic model based on high-accuracy electronic structure calculations using explicitly correlated Gaussians 72 and a simplified treatment of non-adiabatic effects using effective vibrational and rotational masses 73 has been found to provide excellent predictions of ro-vibrational transition frequencies 74 and intensities. 75 This work demonstrated the importance for high accuracy of both using an extensive grid of points in the electronic structure calculation and being careful in how they are fitted to the functional form used to represent the PES. 76 The subsequent focus in these studies has been on including QED effects 77 and improving the treatment of non-adiabatic effects.…”

Orbit-orbit relativistic correction calculated with all-electron molecular explicitly correlated Gaussians

“…Particularly calculations concerning molecules with more than two electrons and/or two nuclei have not been as accurate as the measurements. For a) Electronic address: monika@fizyka.umk.pl b) Electronic address: ludwik@email.arizona.edu example, our recent calculations of the vibrational spectrum of the H + 3 ion, [3][4][5][6] by far the most accurate ever performed, only reached the average accuracy of about 0.1 cm −1 in reproducing the experimental rovibrational frequencies. A part of the reason the H + 3 calculations did not achieve a higher accuracy was an incomplete treatment of the relativistic corrections.…”