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Molecular ions and clusters play a central role in the chemistry of our terrestrial atmosphere and the interstellar
medium. Spectroscopic characterization of these species is highly crucial as it yields fundamental insights on their
structures or dynamics and provides spectral signatures needed to identify their existence. However, generation,
trapping and in situ characterization of these fleeting entities in the laboratory have been persistent challenges
which demand specialized instrumentation. In this concern, a number of studies employing state-of-the-art
techniques will be demonstrated highlighting their implication.
Matrix-isolation spectroscopy technique involving mass-selective deposition of hydrocarbon ions onto
a solid neon (6 Kelvin) allowed to isolated and perform electronic characterization of fulvenallenyl radical (c-
C5H4C≡CH). This resonance stabilized radical is conceived to be the intermediate in the formation of pollutants
like polycyclic aromatic hydrocarbons during the combustion of oils and woods in the atmosphere. Alongside, it
has prospect to be present in interstellar medium as fragment of C60.
The cluster spectroscopy experiments can capture atomistic snapshots of the processes like salt
dissolution or ion hydration, which are relevant for improving climate models. IO3ˉ, the most abundant iodine
species in sea-water, exhibits asymmetric charge distribution which could stabilize two oppositely charged
solvation shells around it. For the unprecedented experimental evidence, microhydration of IO3ˉ is studied by
cryogenic ion trap infrared photodissociation spectroscopy at 13 Kelvin.
Aerosol particle growth begins with the stabilization of a complex of just two molecules, new particle
formation (NPF) stage. However, our understanding of the generation of NPFs is in incipient stage. Helium
nanodroplets technology provides a special condition (0.4 Kelvin) where local minimum structures are often
promoted during molecular association. By employing mass-selective IR spectroscopy, acid-acid complexation
involving intra- and intermolecular hydrogen bonding has been studied. An isomer lying +10 kJ/mol higher than
the global minimum species is stabilized. |