Zheng Shi-Jun

HeI photoelectron spectroscopy of the isoproxy (CH3)2CHO radical

Abstract A continuous (CH 3 ) 2 CHO radical beam is generated by pyrolysis of (CH 3 ) 2 CHONO at 145(±0.5) °C. The HeI photoelectron spectrum of (CH 3 ) 2 CHO is recorded in situ. The IP of (CH 3 ) 2 CHO is 9.70 eV and the spectrum of the X 3 A ″ state of (CH 3 ) 2 CHO + exhibits a vibrational progression of 1200±60 cm −1 . The removal of an electron from the highest occupied molecular orbital 11a ′ , which corresponds to ionization process of ( CH 3 ) 2 CHO + ( 1 A ′ )←( CH 3 ) 2 CHO ( X 2 A ′ ) , leads to a very sharp peak at 10.21 eV. This study provides new experimental and theoretical ionization energies of several ionic states of (CH 3 ) 2 CHO.

Computational studies of s -type weak interactions between NCO/NCS radicals and XY(X = H, Cl; Y = F, Cl, and Br)

The triatomic radicals NCO and NCS are of interest in atmospheric chemistry, and both the ends of these radicals can potentially serve as electron donors during the formation of σ-type hydrogen/halogen bonds with electron acceptors XY (X = H, Cl; Y = F, Cl, and Br). The geometries of the weakly bonded systems NCO/NCS⋯XY were determined at the MP2/aug-cc-pVDZ level of calculation. The results obtained indicate that the geometries in which the hydrogen/halogen atom is bonded at the N atom are more stable than those where it is bonded at the O/S atom, and that it is the molecular electrostatic potential (MEP)—not the electronegativity — that determines the stability of the hydrogen/halogen bond. For the same electron donor (N or O/S) in the triatomic radical and the same X atom in XY, the bond strength decreases in the order Y = F > Cl > Br. In the hydrogen/ halogen bond formation process for all of the complexes studied in this work, transfer of spin electron density from the electron donor to the electron acceptor is negligible, but spin density rearranges within the triatomic radicals, being transferred to the terminal atom not interacting with XY.

Mechanisms and Kinetics of the HOSO+NO Reaction

The mechanism of the reaction between HOSO and NO was investigated at the B3LYP/ 6-311 ++ G(d,p) level of theory. The geometries of the reactants, intermediates, transition states, and products were optimized. The intrinsic reaction coordinates (IRC) were traced and the connecting relationship between the transition states and the reactants, products were confirmed. The single point energies of the species were corrected at the CCSD(T) /6-311++G(d,p) level of theory. The reaction rate constants were calculated over a temperature range of 200-3000 K using classical transition state theory (TST) and canonical vibration transition state theory (CVT) combined with a small-curvature tunneling (SCT) correction. The results showed that the HOSO+NO reaction occurs in both the singlet and triplet reaction channels. The singlet reaction channel is dominant, and HNO and SO2are the main products. The chemical bond changes in the main reaction channel were analyzed by a topological analysis of the electron density.