Back to Search
Start Over
Dynamics and quantum yields of H2 + CH2CO as a primary photolysis channel in CH3CHO.
- Source :
- Physical Chemistry Chemical Physics (PCCP); 7/14/2019, Vol. 21 Issue 26, p14284-14295, 12p
- Publication Year :
- 2019
-
Abstract
- The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CH<subscript>2</subscript>CO) and hydrogen (H<subscript>2</subscript>) molecular products is reported. Acetaldehyde (CH<subscript>3</subscript>CHO) was photolysed in a molecular beam at 305.6 nm and the resulting H<subscript>2</subscript> product characterized using velocity-map ion (VMI) imaging. Resonance-enhanced multiphoton ionization (REMPI), via two-photon excitation to the double-well EF <superscript>1</superscript>Σ+g state, was used to state-selectively ionize the H<subscript>2</subscript> and determine angular momentum distributions for H<subscript>2</subscript> (ν = 0) and H<subscript>2</subscript> (ν = 1). Velocity-map ion images were obtained for H<subscript>2</subscript> (ν = 0 and 1, J = 5), allowing the total translational energy release of the photodissociation process to be determined. Following photolysis of CH<subscript>3</subscript>CHO in a gas cell, the CH<subscript>2</subscript>CO co-fragment was identified, using Fourier transform infrared spectroscopy, by its characteristic infrared absorption at 2150 cm<superscript>−1</superscript>. The measured quantum yield of the CH<subscript>2</subscript>CO + H<subscript>2</subscript> product channel at 305.0 nm is Φ = 0.0075 ± 0.0025 for both 15 Torr of neat CH<subscript>3</subscript>CHO and a mixture with 745 Torr of N<subscript>2</subscript>. Although small, this result has implications for the atmospheric photochemistry of carbonyls and this reaction represents a new tropospheric source of H<subscript>2</subscript>. Quasi-classical trajectory (QCT) simulations on a zero-point energy corrected reaction-path potential are also performed. The experimental REMPI and VMI image distributions are not consistent with the QCT simulations, indicating a non reaction-path mechanism should be considered. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14639076
- Volume :
- 21
- Issue :
- 26
- Database :
- Complementary Index
- Journal :
- Physical Chemistry Chemical Physics (PCCP)
- Publication Type :
- Academic Journal
- Accession number :
- 137299800
- Full Text :
- https://doi.org/10.1039/c8cp06412a