Femtosecond laser pulses are utilized to drive multiple ionization of formic acid dimers and the resulting ions are studied using time-of-flight mass spectrometry. The interaction of formic acid dimer with 200 fs linearly polarized laser pulses of 400 nm with intensities of up to 3.7 × 1015 W/cm2 produces a metastable carbon monoxide trication. Experimental kinetic energy release (KER) measurements of the ions are consistent with molecular dynamics simulations of the Coulomb explosion of a formic acid dimer and suggest that no significant movement occurs during ionization. KER values were recorded as high as 44 eV for CO3+, in agreement with results from a classical Molecular Dynamics simulation of fully ionized formic acid dimers. Potential energy curves for CO3+ are calculated using the multireference configuration interaction (MRCI+Q) method to confirm the existence of an excited metastable 2Σ state with a significant potential barrier with respect to dissociation. This combined experimental and theoretical effort reveals the existence of metastable CO3+ through direct observation for the first time.

Femtosecond laser pulses are utilized to drive multiple ionization in gas-phase formic acid clusters (FA) n . Experimental measurements of the kinetic energy release (KER) of the ions through Coulomb explosion are studied using time-of-flight mass spectrometry and compared to the values recorded from molecules. Upon interacting with 200 fs linearly polarized laser pulses of 400 nm, formic acid clusters facilitate the formation of higher charge states than the formic acid dimer, reaching both C 3+ and O 3+ and also increasing the KER values to several hundred electronvolts in magnitude for such ions. At a lower laser intensity (3.8 × 10 14 W/cm 2 ), we record an enhancement in the signal of the (FA) 5 (H 2 O)H + cluster, which suggests that it has a higher stability, in agreement with previous studies. A molecular dynamics simulation of the Coulomb explosion shows that the highly charged atomic ions arise from larger clusters, whereas the production of CO 3+ is more likely to arise from the molecular case. Thus, the relative production of CO 3+ is reduced in comparison to the highly charged ions upon clustering and is likely due to the higher ionization levels achieved, which facilitate dissociation.

No abstract

No abstract

With increasing concerns over the concentration of carbon dioxide in the atmosphere, new materials are being explored to capture CO 2 for use as a feedstock. The suspected reaction sites of these materials deviates from the bulk phase, such as the quantum confinement of water droplets that happens within pores. The formic acid clusters', (HCOOH) n (H 2 O) m , minimum energy structures show an evolving cage structure with each additional molecule. The n,m = (5,0) cluster exhibits a much greater stability due to its rigid cage-like structure. This cage structure then encapsulates a water molecule to make an even more stable n,m = (5,1) cluster. The interaction of formic acid clusters with 200 fs linearly polarized laser pulses of 800 and 400 nm with intensities up to 1x10 15 W/cm 2 was studied using time-of-flight mass spectrometry, verifying this trend in stability. An enhanced ionization is observed in clusters, leading to the production of triply charged carbon, oxygen, and CO ions that are not observed when only the formic acid molecule is present. Measurements of the kinetic energy release resulting from the Coulomb explosion of clusters are in excellent agreement with our simulations performed over the clusters observed in the mass spectra and suggest that almost no movement occurs during the ionization mechanism. Finally, ultrafast pump-probe spectroscopy was used to investigate how proton transfer dynamics and excited state lifetimes are influenced by the self-solvation of formic acid. These results highlight the role of microsolvation on the excited state dynamics of simple carboxyl groups, specifically formic acid, in producing or capturing carbon dioxide and will help to direct the design of the next generation of carbon capture materials.