Calculation of Anharmonic X-H Stretching Frequencies of Intramolecular Vibrational Chromophores Relevant to Atmospheric Chemistry

Any serious attempt to understand the fundamental physical basis of processes responsible for climate changes must rely on an in-depth understanding of the physics and chemistry of molecular species which constitute Earth’s atmosphere. It is therefore self-understood that new milestones in climate science should aim at the molecular-level understanding of the aforementioned phenomena. In other words, climate science has to undergo a substantial paradigmatic shift, from mesoscale-level models to molecular models. In this context, the establishment of chemistry-climate models should be emphasized, aiming to address at a fundamental molecular level the essential issues such as long-term ozone trends as well as methane lifetime etc. In relation to these issues, organic acids have been thoroughly investigated as possible candidates for precursors in the process of formation of aerosols, which play one of the crucial roles in atmospheric, as well as health sciences. Among the organic acids, formic acid – the simplest representative of this class of compounds, is at the same time the most abundant, and also ubiquitous organic acid in the atmosphere. In the present scientific workflow, through the example of this simplest organic acid we’ll illustrate the approach to compute the anharmonic vibrational frequencies of characteristic X-H intramolecular chromophores which are treatable within 1D approximation (i.e. as one-dimensional anharmonic oscillators). The approach is straightforwardly extendable to an arbitrary X-Y oscillator.