Following our previous work, the A-Band absorption spectrum of the ClSO radical was recorded.  A weak absorption spectrum ranging from 350-480 nm with a peak at 385 nm was observed. Clear vibrational progression was also observed. 

Since ClSO only contain 3 heavy atom, high level calculation with frozen-core approximation is accesible with large basis set. The recorded agreed with simulation at EOMEE-CCSD/ano-pVQZ. Moreover, the electronic structure was revealed based on the molecular orbital analysis, which shows similarity to other sulfinyl radicals (RSO). 

Thionyl chloride, Cl2SO, is widely used in chemical and chemical engineering fields (organic synthesis, lithium battery, detergent as oxidizer and surface treatment agent) as a chlorine source. However, the knowledge about the ClSO radical, generating after a Cl-S bond fission, is stil missing.

For the first time, the UV absorption spectrum of the ClSO radical was recorded in gas phase and was supported by high level ab initio calculation. Moreover, we observed that the ClSO + Cl association reaction to regenerate Cl2SO.

This finding may explain the unusually stability of Cl2SO, and the reported spectrum could be used to understand the unknown reactivity of the ClSO radicals. Moreover, they are complete new data for Venus' atmosphere model and raising the importance of ClSO radical in the coupled chlorine-sulfur chemistry.

Water catalysis reactions has been proposed to possess strong influence in Earth's troposphere due to the high abundance. Although theory has put lots of efforts on predicting the water catalysis effect, we still missing a general picture for understanding across different reactions. 

In this article, we summarized the small Criegee intermediate reactions with hydrogen bonding molecules (H2O, CH3OH and NH3) Some of the reactions show water catalysis effect while the others do not.  

We studies the potential energy diagrams of these reactions and proposed that the entropy cost, bringing the third water molecule to the pre-reactive complex, is ~10 kcal mol-1 under typical tropospheric conditions (298K, RH=50%).  

This "rule of thumb" for estimating the water catalysis effect to systems other than Criegee intermediates are also mentioned. 

This article is a tutorial review and is designed for a student studying physical chemistry, especially for who works on spectroscopic and kinetic measurements. '

We reviewed the reactivity of small Criegee intermediates and, the pro and con of distinct spectroscopic methods as well as the potential questions may encounter in data analysis are discussed.