Advances in spectroscopy and dynamics of small and medium sized molecules and clusters

Abstract

Investigations of the spectroscopy and dynamics of small- and medium-sized molecules and clusters represent a hot topic in atmospheric chemistry, biology, physics, atto- and femto-chemistry and astrophysics. Nowadays, outstanding developments, both theoretical and experimental, have been achieved. The most recent results of these achievements are reviewed here. These molecular systems are studied by means of high-resolution spectroscopic techniques in either the frequency or the time domains. However, they still represent complex molecular systems since they may undergo processes that are still not fully understood in sufficient details. Indeed, electronic and nuclear motions may lead to complex features that are observed experimentally. From a theoretical point of view, these features can only be interpreted if the quantum nature of the atomic nuclei is considered together with the possible couplings between nuclear and electronic degrees of freedom. New developments, from both theoretical and experimental sides, are needed for modeling and engineering applications of outstanding importance. Possible future research directions are discussed.

Chemistry deriving from OOQOOH radicals in alkane low-temperature oxidation: A first combined theoretical and electron-ion coincidence mass spectrometry study

“…Subsequently, we performed single point (SP) computations using the costly (R)CCSD(T)-F12/augcc-pVTZ method as implemented in MOLPRO 2015 [17]. While PBE0/aug-cc-pVDZ(opt) level leads to AIEs off by more than 0.2 eV for medium-sized molecules, the composite scheme PBE0/aug-cc-pVDZ(opt)//(R)CCSD(T)-F12/aug-cc-pVTZ(SP) allows accurate derivation of these AIEs (to within a maximum of ± 0.02 eV) as discussed previously [18] (see a comparison of the values obtained with both methods in Table S1 (SM)). Afterwards, we simulated the vibrationally-resolved Franck-Condon photoelectron spectra (FCPS), for the ion ground state of the species listed in In a second step, the origin bands were shifted in energy to coincide with the respective PBE0/aug-cc-pVDZ(opt)//(R)CCSD(T)-F12/aug-cc-pVTZ(SP) AIEs.…”

“…Table 1 also gives the optimized structures of the 10 KHP isomers and their AIEs as computed at the composite scheme PBE0(opt)/aug-cc-pVDZ//(R)CCSD(T)-F12/aug-cc-pVTZ(SP) level. As established [18], the composite scheme is more reliable and we use its results for the assignment of the experimental spectra. Table 1 shows that all 10…”

Isomer-sensitive characterization of low temperature oxidation reaction products by coupling a jet-stirred reactor to an electron/ion coincidence spectrometer: case of n-pentane

“…[69] Previous benchmarking by comparison to experimental results showed that the composite scheme PBE0/aug-cc-pVDZ(opt)//(R)CCSD(T)-F12/aug-cc-pVTZ(SP) allows accurate derivation of ionization energies of medium-sized molecular systems (to within ± 0.01 eV). [55,[70][71][72][73][74] Afterwards, the computed spectra were shifted in energy so that the first peak fits with adiabatic ionization energy as computed at the PBE0/aug-cc-pVDZ(opt)//(R)CCSD(T)-F12/augcc-pVTZ(SP) level. All the simulated vibrationally resolved electronic spectra in this work are given in the Supplementary Material.…”

From atoms to aerosols: probing clusters and nanoparticles with synchrotron based mass spectrometry and X-ray spectroscopy

“…2,3 With the acquisition of new hardware, this beamline now has a dedicated port for soft X-rays, and we hope to show in this perspective, that a seamless transition is occurring in the science and methods employed in probing chemical dynamics and reactivity from the gas to the condensed phase. While we focus on using synchrotron radiation to probe chemical transformations in clusters and nanoparticles, the interested reader may find recent reviews of spectroscopy and dynamics of molecules and clusters, 4 ultrafast X-ray probing in chemical dynamics 5 , and the study of clusters and nanoparticles at a free electron laser (FEL) 6 illuminating and can act as a contrast to science that is being performed with a 25 year old instrument.…”