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Strong-field ionization of CH3Cl using femtosecond laser pulses, and the subsequent two-body dissociation of CH3Cl2+ along Hn+ (n = 1–3) and HCl+ forming pathways, have been experimentally studied in a home-built COLTRIMS (cold target recoil ion momentum spectrometer) setup. The single ionization rate of CH3Cl was obtained experimentally by varying the laser intensity from 1.6 × 1013 W cm−2 to 2.4 × 1014 W cm−2 and fitted with the rate obtained using the MO-ADK model. Additionally, the yield of Hn+ ions resulting from the dissociation of all charge states of CH3Cl was determined as a function of intensity and pulse duration (and chirp). Next, we identified four two-body breakup pathways of CH3Cl2+, which are H+ + CH2Cl+, H2+ + CHCl+, H3+ + CCl+, and CH2+ + HCl+, using photoion–photoion coincidence. The yields of the four pathways were found to decrease on increasing the intensity from I = 4.2 × 1013 W cm−2 to 2I = 8.5 × 1013 W cm−2, which was attributed to enhanced ionization of the dication before it can dissociate. As a function of pulse duration (and chirp), the Hn+ forming pathways were suppressed, while the HCl+ forming pathway was enhanced. To understand the excited state dynamics of the CH3Cl dication, which controls the outcome of dissociation, we obtained the total kinetic energy release distributions of the pathways and the two-dimensional coincidence momentum images and angular distributions of the fragments. We inferred that the Hn+ forming pathways originate from the dissociation of CH3Cl dications from weakly attractive metastable excited states having a long dissociation time, while for the HCl+ forming pathway, the dication dissociates from repulsive states and therefore, undergoes rapid dissociation. Finally, quantum chemical calculations have been performed to understand the intramolecular proton migration and dissociation of the CH3Cl dication along the pathways mentioned above. Our study explains the mechanism of Hn+ and HCl+ formation and confirms that intensity and pulse duration can serve as parameters to influence the excited state dynamics and hence, the outcome of the two-body dissociation of CH3Cl2+. [ABSTRACT FROM AUTHOR]

Numerical studies were conducted on the hydrodynamics of a freely falling rigid sphere in bounded and unbounded water domains to investigate the drag coefficient, normalized velocity, pressure coefficient, and skin friction coefficient as a function of dimensionless time. The bounded domain was simulated by bringing the cylindrical water container's wall closer to the impacting rigid sphere and linking it to the blockage ratio (BR), defined as the ratio of the projection area of a freely falling sphere to that of the cross-sectional area of the cylindrical water container. Six cases of bounded domains (BR = 1%, 25%, 45%, 55%, 65%, and 75%) were studied. However, the unbounded domain was considered with a BR of 0.01%. In addition, the kk-ω shear stress transport (SST) turbulence model was used, and the computed results of the bounded domain were compared with those of other studies on unbounded domains. In the case of the bounded domain, which has a higher value of BR, a substantial reduction in normalized velocity and an increase in the drag coefficient were found. Moreover, the bounded domain yielded a significant increase in the pressure coefficient when the sphere was half-submerged; however, an insignificant effect was found on the skin friction coefficient. In the case of the unbounded domain, a significant reduction in the normalized velocity occurred with a decrease in the Reynold number (Re), whereas the drag coefficient increases with a decrease in Reynolds number. [ABSTRACT FROM AUTHOR]

Climate change and global warming are the visible consequences of the increased amount of carbon dioxide (CO2) in the atmosphere. Among the various sources of anthropogenic CO2 emission, the diesel engine has a significant contribution. The development of a reliable system to efficiently minimize CO2 emissions from diesel engines to the safest level is lacking in the open literature. Therefore, a comprehensive multidisciplinary approach has been applied in this paper to investigate the efficacy of the post-combustion carbon capture (PCC) process for the diesel engine. The experiments have been performed on the exhaust of a direct injection diesel engine at five different brake powers with blends of aqueous ammonia (AQ_NH3), monoethanolamine (MEA), N,N-dimethylethanolamine (DMEA), and 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) ionic liquid (IL) as an absorbent for CO2 capture. The reaction mechanism of these absorbent with CO2 are also studied by the geometrical, energetical, MESP, frontier molecular orbitals, and NBO analysis using the first-principles density functional theory (DFT) calculations. The maximum CO2 absorption efficiency of almost 97% was achieved for the blend consisting of 67% of AQ_NH3 and 33% of MEA. Moreover, AQ_MEA and blend of AQ_NH3, DMEA, and C2mim BF4 ionic liquid showed 96% and 94% CO2 absorption efficiency, respectively. [ABSTRACT FROM AUTHOR]

Strong-field ionization induces various complex phenomena like bond breaking, intramolecular hydrogen migration, and bond association in polyatomic molecules. The H-atom migration and bond formation in CH3OH induced by intense femtosecond laser pulses are investigated using a Velocity Map Imaging (VMI) spectrometer. Various laser parameters like intensity (1.5 × 1013 W cm−2–12.5 × 1013 W cm−2), pulse duration (29 fs and 195 fs), wavelength (800 nm and 1300 nm), and polarization (linear and circular) can serve as a quantum control for hydrogen migration and the yield of Hn+ (n = 1–3) ions which have been observed in this study. Further, in order to understand the ejection mechanism of the hydrogen molecular ions H2+ and H3+ from singly-ionized CH3OH, quantum chemical calculations were employed. The dissociation processes of CH3OH+ occurring by four dissociative channels to form CHO+ + H3, H3+ + CHO, CH2+ + H2O, and H2O+ + CH2 are studied. Using the combined approach of experiments and theory, we have successfully explained the mechanism of intramolecular hydrogen migration and predicted the dissociative channels of singly-ionized CH3OH. [ABSTRACT FROM AUTHOR]

We present a study of the impact of water on the size‐ and electronegativity‐dependent hydrogen bonds between cation and anion of imidazolium‐based ionic liquids (ILs) with halide anions. We have combined Raman spectroscopy with density functional theory (DFT) computations to characterize the intermolecular associations of cation–anion–water moieties. The Raman band at ~1,422 cm−1, which is assigned to the ν(N─CH2─CH3) vibration of the ethyl chain in the neat ion pairs (pure ion pairs), is blue shifted by +7, +4, and +3 cm−1 for 1‐ethyl‐3‐methylimidazolim (C2mim) cation‐based C2mim X ion pairs with X = Cl, Br, and I, respectively, in a water‐rich environment. Simultaneously, upon dilution, a new peak at ~1,438 cm−1 starts to appear at the high‐wavenumber side with continuously increasing intensity. These significant perturbations of the ν(N─CH2─CH3) vibrational mode in water environment are a clear indication of the change in the alkyl chain conformation. Further, the relative intensities of the Raman bands at ~2,946 and ~2,950 cm−1 corresponding to νs (CH2) and νas (CH3) of the ethyl chain, respectively, were significantly changed upon dilution, which also confirms the conformational change of the alkyl chain. The Raman band belonging to the C4/5─H stretch mode was significantly blue shifted by +33, +41, and +42 cm−1 going from the studied neat ion pairs having Cl, Br, and I anions to the corresponding water mixtures, respectively. Significant changes were also observed for the ν(C2─H) vibrational mode of the ion pairs in water environment; here, we observed blue shifts of +60, +51, and +50 cm−1 for ion pairs having Cl, Br, and I anions, respectively. These results confirm the weakening of the ion‐pair interaction due to the interaction with water molecules. In contrast to the ILs with halide anions, C2mim BF4 does not show any variation in the Raman peak positions upon dilution. Experimental results are nicely supported by the results of DFT calculations, and a sensible connection was established. [ABSTRACT FROM AUTHOR]