Molecular spectroscopy techniques are unique tools to probe molecular systems non-invasively and investigate their structure, properties, and dynamics in different environments and physicochemical conditions. Different spectroscopic techniques and their combination can lead to a more comprehensive picture of investigated systems. However, the increasing sophistication of these experimental techniques makes it more and more complex and difficult to interpret the results without the help of computational chemistry. As a consequence, computational molecular spectroscopy has progressively changed from a highly specialized field to a general tool also employed by experimentally-oriented researchers. Computational spectroscopy, born as a branch of quantum chemistry for providing predictions of spectroscopic properties and features, evolved as an independent field. In this Primer, we focus on the characterization of medium-sized molecular systems by means of different spectroscopic techniques. We first provide essential information about the characteristics, accuracy and limitations of the available computational approaches, and select examples with the aim of illustrating general trends, that is outcomes of general validity that can be used for modeling spectroscopic phenomena. We emphasize the need for estimating error bars and limitations, coupling accuracy with interpretability, and discuss the results in terms of widely recognized chemical concepts.
We present the first detection of (Z)-1,2-ethenediol, (CHOH)2, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693−0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 ± 0.1) × 1013 cm−2, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10−10. The abundance ratio between glycolaldehyde and (Z)-1,2-ethenediol is ∼5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H2CO, CHOH, or CH2CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH2CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.
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