Our new paper describing the kinetics of reactions of CH2OO with ketones and diketones has been published in the Journal of Physical Chemistry A. We find rate constants for the β-diketone reactions that are similar to that of acetone, while those for the α-diketones are around 30 times larger. The trends are interpreted using frontier molecular orbital theory.
You can read the paper here: 10.1021/acs.jpca.1c05280
The results of velocity-map imaging experiments characterizing the vibrational predissociation dynamics of HCl dimer have been published in the Journal of Chemical Physics. The free and bound HCl stretch overtones were excited using an infrared laser and the monomer fragments detected using 2+1 REMPI. The correlated product-pair distributions show a strong propensity to maximize rotational excitation and minimize the recoil translational energy. The experimental results are compared with the predictions of various predissociation models.
You can read the paper here: 10.1063/5.0003652
We explore the UV photofragmentation dynamics of acetaldehyde cation in our latest paper published in PCCP. Single-photon VUV ionization was used to prepare cold acetaldehyde cations that are subsequently excited (and fragmented) by UV radiation. The photochemistry is surprisingly rich; we use velocity-map ion imaging to characterize four different photofragmentation channels across a broad range of wavelengths. The experiments are supported by complementary ab initio calculations. The article will appear in a special themed issue of PCCP on Photodissociation and Reaction Dynamics that will be published to celebrate the 65th birthday of former University of Bristol colleague Prof. Mike Ashfold.
You can read the paper here: 10.1039/c8cp06640j
Our latest photodissociation dynamics paper has been published in PCCP. The new paper describes ion imaging and photofragment excitation spectroscopy experiments exploring the photochemistry of acetone. We identify ketene as a new primary photoproduct following excitation to S1 and suggest that a roaming mechanism may be responsible. The radical channel forming methyl and acetyl is characterized over a broad range of wavelengths and is dominated by dissociation on the T1 surface following intersystem crossing. Time-resolved measurements using a ps laser system at 266 nm, find an intersystem crossing rate that is surprisingly around six times slower than in acetaldehyde.
You can read the paper here: 10.1039/c7cp07320h
Our new paper published in J. Phys. Chem. A. combines broadband transient absorption spectroscopy with complementary ab initio calculations to explore the kinetics of the reactions of the simplest Criegee intermediate with a series of alcohols. The results of this study provide new insights into trends in Criegee reactivity.
You can read the paper here: 10.1021/acs.jpca.7b09773
Our most recent paper published in Phys. Chem. Chem. Phys. explores the photochemistry of chlorodiiodomethane (CHI2Cl), a precursor of chlorinated Criegee intermediates. Velocity map ion imaging experiments and high-level ab initio calculations were employed to characterize the photodissociation dynamics of CHI2Cl over a range of wavelengths. We further used transient absorption spectroscopy to measure the UV absorption spectrum of a chlorinated Criegee intermediate, ClCHOO, produced from the reaction of CHICl with O2.
Check out our paper here: 10.1039/C7CP06532A
This article was selected as part of the 2017 PCCP HOT Articles themed collection.
Our latest paper, exploring the photochemistry of acetaldehyde to form CH3 + HCO across a broad range of wavelengths, has been published in PCCP. We used a combination of time-resolved ion imaging, with nanosecond and picosecond pulsed lasers, and photofragment excitation action spectroscopy to identify three distinct dissociation mechanisms. At long wavelengths, dissociation occurs statistically on the S0 surface after many tens of nanoseconds. Dissociation at intermediate wavelengths is dominated by relatively fast dissociation on the T1 surface, leading to fast-moving CH3 radicals. At short wavelengths, a new pathway opens that is assigned to dissociation on the S0 surface, accessed via a conical intersection.
The article can be accessed here: 10.1039/c7cp02573d
This article was selected as part of the 2017 PCCP HOT Articles themed collection.
Our new paper published in J. Phys. Chem. A uses PHOtoFragment EXcitation (PHOFEX) spectroscopy to pick apart the first absorption band of OCS, the most abundant sulfur-containing molecule in the atmosphere. The PHOFEX spectra obtained probing electronically excited S(1D) and ground state S(3P) atoms are distinctly different; the former is broad and unstructured, while the latter shows distinct resonances that can be attributed to vibrational structure following direct excitation of a quasi-bound triplet state.
The article can be found here: 10.1021/acs.jpca.6b06060
Our new paper on the kinetics of reactions between the simplest Criegee intermediate, CH2OO, and the inorganic acids HCl and HNO3 has been published as a “hot paper” in Angewandte Chemie International Edition. The reaction with HNO3 in particular is likely to be an important sink in polluted environments. You can read it here: 10.1002/anie.201604662
UPDATE: A news article highlighting our paper has been published on ChemistryViews.
We have two new papers published online in PCCP this week.
The first is another collaborative paper with UCI colleague Prof. Benny Gerber and his University of Helsinki team, that follows up on our work on the spectroscopy of the simplest Criegee intermediate, CH2OO. It describes trajectory calculations that explore the excited state dynamics. Read it here: 10.1039/c6cp00807k
The second paper describes a velocity-map ion imaging study of the photodissociation dynamics of diiodomethane (CH2I2). Experimental measurements are interpreted with the help of high-level ab initio calculations by Dr. Grant Hill of the University of Sheffield. Read it here: 10.1039/c6cp01063f