Computational vibrational spectroscopy for the detection of molecules in space

Quantum-mechanical Rotational and Vibrational Signatures of Astrophyscially relevant Gas-Phase Stereo-isomeric Species of Leucine

“…Note that for these calculations, a quartic force field (QFF) is deployed for the inter-nuclear potential in the 'Watson' Hamiltonian so as to account for ro-vibrational interactions. 9,21 Further, for the computation of vibrational frequencies, the anharmonicity is estimated at the level of the second order vibrational perturbation theory (VPT2) which is basically rooted in the Rayleigh-Schrödinger perturbation theory. 43,44 Note that the inclusion of anharmonic effects actually contribute towards an accurate estimation of both vibrational and rotational parameters, 21 by aiding the evaluation of rotational constants associated with vibrationally averaged ground state.…”

“…9,21 Further, for the computation of vibrational frequencies, the anharmonicity is estimated at the level of the second order vibrational perturbation theory (VPT2) which is basically rooted in the Rayleigh-Schrödinger perturbation theory. 43,44 Note that the inclusion of anharmonic effects actually contribute towards an accurate estimation of both vibrational and rotational parameters, 21 by aiding the evaluation of rotational constants associated with vibrationally averaged ground state. Besides this, the anharmonic calculations also provide the centrifugal distortion constants which are estimated employing Watson's A-reduced Hamiltonian in irreducible (I r ) representation.…”

“…Therefore, the spectroscopic data computed in the rotational and infrared regions is quite valuable in sorting the complex spectroscopic information received from the outer space as well as from the laboratories mimicking the outer space environment. 21 Not only this, the interstellar spectroscopic studies are providing unique opportunities to broaden up our understanding of physical and chemical characteristics of the universe. 22,23 The various regions of ISM are speculated to be associated with all the core functional groups of organic prominence, thereby, acting as significant players in the extra-terrestrial formation of bio-molecules.…”

A large-scale approach to modelling Biosignatures: First Steps

“…We use this methodology as historically quartic force fields have been used for defining the potential of the inter-nuclear Hamiltonian. In particular it is used as a tool for analyzing and producing rovibrational spectra for molecules of interest to astrophysical observation (Fortenberry & Lee 2019).…”

Pathways to Detection of Strongly-Bound Inorganic Species: The Vibrational and Rotational Spectral Data of AlH2OH, HMgOH, AlH2NH2, and HMgNH2

“…In any case, their spectral features will be computed via quartic force fields (QFFs) which are fourth-order Taylor series expansions of the internuclear Hamiltonian. Their utilization defined with accurate electronic structure methods have previously produced anharmonic fundamental vibrational frequencies to within 0.70% error as well as B and C rotational constants to within 0.12% error of gas phase experiment (Huang et al, 2011;Fortenberry et al, 2012a, Fortenberry et al, 2012bZhao et al, 2014;Morgan and Fortenberry, 2015;Theis and Fortenberry, 2016;Bizzocchi et al, 2017;Kitchens and Fortenberry, 2016;Fortenberry and Francisco, 2017;Fuente et al, 2017;Wagner et al, 2018;Fortenberry and Lee, 2019;Gardner et al, 2021). The accuracy of such methods has led to the first interstellar observation of HOCO + in the ] 5 1 state (Bizzocchi et al, 2017) as well as the first laboratory observation of ArOH + (Wagner et al, 2018), both based on previously existing quantum chemical data produced in our group (Fortenberry et al, 2012b;Theis and Fortenberry, 2016).…”