Photolysis Dynamics Laser Chemistry Lab

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By using time-resolved Fourier-transform infrared emission spectroscopy, the fragments of HCN(v 1, 2) and CO(v 1-3) are detected in one-photon dissociation of acetyl cyanide (CH 3COCN) at 308 nm. The S 1(A ″), 1(n O, π CO) state at 308 nm has a radiative lifetime of 0.46 ± 0.01 μs, long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of Ar collision-induced internal conversion is estimated to be (1-7) × 10 -12 cm 3 molecule -1 s -1. The measurements of O 2 dependence exclude the production possibility of these fragments via intersystem crossing. The high-resolution spectra of HCN and CO are analyzed to determine the ro-vibrational energy deposition of 81 ± 7 and 32 ± 3 kJmol, respectively. With the aid of ab initio calculations, a two-body dissociation on the energetic ground state is favored leading to HCN CH 2CO, in which the CH 2CO moiety may further undergo secondary dissociation to release CO. The production of CO 2 in the reaction with O 2 confirms existence of CH 2 and a secondary reaction product of CO. The HNC fragment is identified but cannot be assigned, as restricted to a poor signal-to-noise ratio. Because of insufficient excitation energy at 308 nm, the CN and CH 3 fragments that dominate the dissociation products at 193 nm are not detected. © 2012 American Institute of Physics.

By employing time-resolved Fourier transform infrared emission spectroscopy, the fragments HCl (v=1-3), HBr (v=1), and CO (v=1-3) are detected in one-photon dissociation of 2-bromopropionyl chloride (CH3CHBrCOCl) at 248 nm. Ar gas is added to induce internal conversion and to enhance the fragment yields. The time-resolved high-resolution spectra of HCl and CO were analyzed to determine the rovibrational energy deposition of 10.0A ±0.2 and 7.4A ±0.6 kcal mol-1, respectively, while the rotational energy in HBr is evaluated to be 0.9A ±0.1 kcal mol-1. The branching ratio of HCl(v>0)/HBr(v>0) is estimated to be 1:0.53. The bond selectivity of halide formation in the photolysis follows the same trend as the halogen atom elimination. The probability of HCl contribution from a hot Cl reaction with the precursor is negligible according to the measurements of HCl amount by adding an active reagent, Br2, in the system. The HCl elimination channel under Ar addition is verified to be slower by two orders of magnitude than the Cl elimination channel. With the aid of ab initio calculations, the observed fragments are dissociated from the hot ground state CH3CHBrCOCl. A two-body dissociation channel is favored leading to either HCl+CH3CBrCO or HBr+CH2CHCOCl, in which the CH 3CBrCO moiety may further undergo secondary dissociation to release CO. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this study, 2D graphene oxide nanosheets (GONS) were synthesized and characterized by XRD, Raman, SEM, FE-SEM, TEM, XPS, TGA, UV-vis and FTIR spectral techniques. The efficiency of eosin yellow (EY) dye adsorption on the GONS under various experimental parameters such as contact time, pH and temperature was investigated. Adsorption kinetic data were characterized appropriately using pseudo second-order-kinetics and intraparticle diffusion methods. Free energy of adsorption (ΔG0), enthalpy (ΔH0), entropy (ΔS0) changes, activation energy and Arrhenius factors were also calculated. The endothermic and spontaneous nature of the adsorption process was confirmed by the positive value of the enthalpy change (ΔH0) and the negative value of free energy change (ΔG0). The adsorption mechanism was investigated by FTIR spectra of GONS before and after adsorption of EY dye molecules. The remarkable adsorption capacity of EY onto the GONS can be attributed to the various adsorption interaction mechanisms such as hydrogen bonding, π-π electron, and electrostatic interactions. The maximum adsorption capacity for EY was calculated to be 217.33 mg g-1. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim