Room temperature line lists for CO2 symmetric isotopologues with ab initio computed intensities

Oleg L. Polyansky,Jonathan Tennyson,Sergei A. Tashkun,Lorenzo Lodi,Emil J. Zak,Valery I. Perevalov,Nikolay F. Zobov

doi:10.1016/j.jqsrt.2016.11.022

Abstract

Remote sensing experiments require high-accuracy, preferably sub-percent, line intensities and in response to this need we present computed room temperature line lists for six symmetric isotopologues of carbon dioxide: 13C16O2, 14C16O2, 12C17O2, 12C18O2, 13C17O2 and 13C18O2, covering the range 0–8000cm−1. Our calculation scheme is based on variational nuclear motion calculations and on a reliability analysis of the generated line intensities. Rotation–vibration wavefunctions and energy levels are computed using the DVR3D software suite and a high quality semi-empirical potential energy surface (PES), followed by computation of intensities using an ab initio dipole moment surface (DMS). Four line lists are computed for each isotopologue to quantify sensitivity to minor distortions of the PES/DMS. Reliable lines are benchmarked against recent state-of-the-art measurements and against the HITRAN2012 database, supporting the claim that the majority of line intensities for strong bands are predicted with sub-percent accuracy. Accurate line positions are generated using an effective Hamiltonian. We recommend the use of these line lists for future remote sensing studies and their inclusion in databases.

Highlights

Remote sensing of carbon dioxide for atmospheric applications requires a detailed knowledge of the rotational-vibrational spectra of all its major isotopologues
In this work we aim to provide highly accurate line intensities in the 0 – 8000 cm−1 spectral region together with reliable semi-empirical line positions for six symmetric isotopologues of carbon dioxide; five naturally abundant: 636, 727, 737, 828, 838 and one radioactive (646)
In the present study we compute new line lists for six symmetric isotopologues of carbon dioxide: 13C16O2, 14C16O2, 12C17O2, 12C18O2, 13C17O2 and 13C18O2. Detailed comparisons with both the theoretical and experimental works indicate the high accuracy of the line intensities resulting from our ab initio dipole moment surface (DMS)

Summary

Introduction

Remote sensing of carbon dioxide for atmospheric applications requires a detailed knowledge of the rotational-vibrational spectra of all its major isotopologues. It is commonly believed that such measurements should be supported by reference line intensities of 1% accuracy or better [1]. This is the main requirement for successful interpretation of data from the NASA Orbiting Carbon Observatory 2 (OCO-2) space mission, which is designed to monitor the concentration of carbon dioxide in Earth’s atmosphere. Concentration measurements of trace compounds require very accurate line positions, intensities and line profiles of several isotopologues at the same time

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