A general variational approach for computing rovibrational resonances of polyatomic molecules. Application to the weakly bound H2He+ and H2⋅CO systems

Abstract

The quasi-variational quantum chemical protocol and code GENIUSH [E. Mátyus et al., J. Chem. Phys. 130, 134112 (2009) and C. Fábri et al., J. Chem. Phys. 134, 074105 (2011)] has been augmented with the complex absorbing potential (CAP) technique, yielding a method for the determination of rovibrational resonance states. Due to the effective implementation of the CAP technique within GENIUSH, the GENIUSH-CAP code is a powerful tool for the study of important dynamical features of arbitrary-sized molecular systems with arbitrary composition above their first dissociation limit. The GENIUSH-CAP code has been tested and validated on the HHe cation: the computed resonance energies and lifetimes are compared to those obtained with a previously developed triatomic rovibrational resonance-computing code, DFOPI-CCS [T. Szidarovszky and A. G. Császár Mol. Phys. 111, 2131 (2013)], utilizing the complex coordinate scaling method. A unique feature of the GENIUSH-CAP protocol is that it allows the simple implementation of reduced-dimensional dynamical models. To prove this, resonance energies and lifetimes of the H⋅CO van der Waals complex have been computed utilizing a four-dimensional model (freezing the two monomer stretches), and a related potential energy surface, of the complex.

Cationic Noble-Gas Hydrides: From Ion Sources to Outer Space

“…The NgH + 2 possess linear Ng-H-H + connectivities, and their potential wells (see Table 1) are deep enough Koner et al, 2019) to sustain numerous vibrational and rovibrational states. The latter were accurately estimated even recently Papp et al, 2017Papp et al, , 2018Szidarovszky and Yamanouchi, 2017), also in the intriguing prospect of actual detection of natural NgH + 2 . Some general warnings in this regard come, however, from the information already available, in particular on the gas-phase ion chemistry of Ar/H 2 mixtures (Bedford and Smith, 1990;Hvistendahl et al, 1990;Koyanagi et al, 2000).…”

Fingerprints of microscopic superfluidity in HHen+ clusters

“…These clusters would involve H + 2 or H + 3 in the core. H 2 He + has been the subject of some advanced theoretical studies [68,69,124], while H 3 He + has already been synthesised and investigated spectroscopically in the same trap machine as used in this study [67]. Further quantum chemical and low-as well as high-resolution spectroscopic studies on these species are planned in our laboratories.…”

Accuracy and Reliability in the Simulation of Vibrational Spectra: A Comprehensive Benchmark of Energies and Intensities Issuing From Generalized Vibrational Perturbation Theory to Second Order (GVPT2)

“…For the specific case of vibrational spectroscopies, this requirement necessarily includes the treatment of anharmonicity in nuclear motions, with the possible inclusion of the rotational substructure (Biczysko et al, 2018;Puzzarini et al, 2019). Beyond very sophisticated rovibronic models, still limited in practice to diatomic or triatomic systems in standard applications (Carter et al, 1990(Carter et al, , 2000Császár et al, 2012;Mitrushchenkov, 2012;Nauts and Lauvergnat, 2012;Yurchenko et al, 2016), variational methods in conjunction with electronic structure calculations at the coupled cluster (CC) or configuration interaction (CI) levels represent a gold standard (Biczysko et al, 2003;Mátyus et al, 2009;Papp et al, 2017;Erfort et al, 2020). Indeed, variational approaches can in principle be systematically improved to reach any target accuracy, by using higherorder force fields through an extensive sampling of the potential energy surface (PES).…”