Tag Archives: paper

Acetone photodissociation paper appears in PCCP

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

New Criegee paper in JPCA

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

New imaging paper published in PCCP

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.

Time-resolved photochemistry paper in PCCP

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.

OCS PHOFEX paper published in J. Phys. Chem. A

OCS PHOFEXOur 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

“Hot Paper” in Angewandte Chemie

CH2OO + acids

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.

Pair of papers in PCCP

We have two new papers published online in PCCP this week.

Criegee intermediate dynamicsDiiodomethane photochemistry

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

Criegee intermediate spectroscopy paper published in PCCP

CH2OO B-X spectrum

Our paper on the spectroscopy of the simplest Criegee intermediate, produced in collaboration with UCI colleague Prof. Benny Gerber, has been published in Phys. Chem. Chem. Phys. We have used broadband absorption and cavity ring-down spectroscopy to measure absolute (and temperature-dependent) absorption cross sections for CH2OO in the visible/near UV.

The article can be found here: 10.1039/C5CP04977F

New paper published in J. Phys. Chem. A

IO kinetics

Our first paper on the important CH2I + O2 reaction has been published in J. Phys. Chem. A. We used cavity ring-down spectroscopy to study the kinetics of IO formation, finding evidence for production both directly and sequentially after first forming CH2OO + I. The direct mechanism appears to depend on the degree of internal energy of the photolytically generated CH2I radical; a cautionary tale for laboratory kinetics studies that use this method to generate radical species.

You can read it here: 10.1021/acs.jpca.5b05058