High-resolution absorption cross sections of formaldehyde at wavelengths from 313 to 320 nm. 2005

Francis D Pope, and Carina A Smith, and Michael N R Ashfold, and Andrew J Orr-Ewing
School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK.

Absorption cross sections have been measured for the 2(0)(2)4(0)(3) and 2(0)(3)4(0)(1) vibrational bands of the [formula: see text] electronic transition of formaldehyde in the wavelength range 313-320 nm. Accurate values are of considerable importance for atmospheric monitoring and to understand the photochemistry of this compound. The 0.10 cm(-1) FWHM wavenumber resolution of the experiments is determined by the bandwidth of the ultraviolet laser used, and is a factor of 10 or more higher than any previously reported data. The absorption cross section data are thus obtained at a spectrometer resolution close to the Doppler broadening limit at 294 K of 0.07 cm(-1) FWHM, for isolated rotational lines, but lifetime broadening effects contribute a further approximately 0.5 cm(-1) of width. Our spectral resolution is thus higher than required to resolve the sharpest spectral features and, as a consequence, the cross sections peak at greater values than previous studies of these structured rovibronic bands conducted at much lower spectrometer resolutions. Previous data can be quantitatively reproduced by convolution of the newly obtained spectra with lower-resolution instrument functions. Pressure broadening of regions of the spectra in the presence of up to 500 Torr of N2 is examined and the effects on peak absorption cross sections are very small. The influence of reduced temperature on the spectrum is also explored through experimental measurements and spectral simulations.

UI MeSH Term Description Entries
D007834 Lasers An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum. Masers,Continuous Wave Lasers,Pulsed Lasers,Q-Switched Lasers,Continuous Wave Laser,Laser,Laser, Continuous Wave,Laser, Pulsed,Laser, Q-Switched,Lasers, Continuous Wave,Lasers, Pulsed,Lasers, Q-Switched,Maser,Pulsed Laser,Q Switched Lasers,Q-Switched Laser
D010126 Ozone The unstable triatomic form of oxygen, O3. It is a powerful oxidant that is produced for various chemical and industrial uses. Its production is also catalyzed in the ATMOSPHERE by ULTRAVIOLET RAY irradiation of oxygen or other ozone precursors such as VOLATILE ORGANIC COMPOUNDS and NITROGEN OXIDES. About 90% of the ozone in the atmosphere exists in the stratosphere (STRATOSPHERIC OZONE). Ground Level Ozone,Low Level Ozone,Tropospheric Ozone,Level Ozone, Ground,Level Ozone, Low,Ozone, Ground Level,Ozone, Low Level,Ozone, Tropospheric
D004581 Electronics The study, control, and application of the conduction of ELECTRICITY through gases or vacuum, or through semiconducting or conducting materials. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Electronic
D004777 Environment The external elements and conditions which surround, influence, and affect the life and development of an organism or population. Environmental Impact,Environmental Impacts,Impact, Environmental,Impacts, Environmental,Environments
D005557 Formaldehyde A highly reactive aldehyde gas formed by oxidation or incomplete combustion of hydrocarbons. In solution, it has a wide range of uses: in the manufacture of resins and textiles, as a disinfectant, and as a laboratory fixative or preservative. Formaldehyde solution (formalin) is considered a hazardous compound, and its vapor toxic. (From Reynolds, Martindale The Extra Pharmacopoeia, 30th ed, p717) Formalin,Formol,Methanal,Oxomethane
D005579 Fossil Fuels Any combustible hydrocarbon deposit formed from the remains of prehistoric organisms. Examples are petroleum, coal, and natural gas. Fossil Fuel,Fuel, Fossil,Fuels, Fossil
D000388 Air The mixture of gases present in the earth's atmosphere consisting of oxygen, nitrogen, carbon dioxide, and small amounts of other gases.
D012399 Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Clinorotation,Clinorotations,Rotations
D013056 Spectrophotometry, Ultraviolet Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Ultraviolet Spectrophotometry
D014732 Vibration A continuing periodic change in displacement with respect to a fixed reference. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Vibrations

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