The Primary Photochemical Process In Simple Ketones

Noyes, W. Albert; Porter, Gerald B.; Jolley, J. Eric

doi:10.1021/cr50007a003

Cited by 128 publications

(43 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, the linear dependence of the absorption with concentration at 340 nm, and particularly at 350 nm, provides strong evidence for the reliability of our cross-sections at these and similar wavelengths. Small undulations are visible in the IBBCEAS absorption spectra and probably correspond to the tail-end of small absorption structures that have been known for a long time (Noyes et al, 1956).…”

Section: Ketone Spectramentioning

confidence: 83%

A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases

Chen

Venables

2011

Atmos. Meas. Tech.

View full text Add to dashboard Cite

Abstract. Accurate absorption spectra of gases in the nearultraviolet (300 to 400 nm) are essential in atmospheric observations and laboratory studies. This paper describes a novel incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for measuring very weak absorption spectra from 335 to 375 nm. The instrument performance was validated against the 3 B 1 -X 1 A 1 transition of SO 2 . The measured absorption varied linearly with SO 2 column density and the resulting spectrum agrees well with published spectra. Using the instrument, we report new absorption cross-sections of O 3 , acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably. In the absorption minimum between the Huggins and Chappuis bands, our absorption spectra fall at the lower range of reported ozone absorption crosssections. The spectra of the ketones agree with prior spectra at moderate absorptions, but differ significantly at the limits of other instruments' sensitivity. The collision-induced absorption of the O 4 dimer at 360.5 nm was also measured and found to have a maximum cross-section of ca. 4.0 × 10 −46 cm 5 molecule −2 . We demonstrate the application of the instrument to quantifying low concentrations of the shortlived radical, BrO, in the presence of stronger absorptions from Br 2 and O 3 .

show abstract

Section: Ketone Spectramentioning

confidence: 83%

A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases

Chen

Venables

2011

Atmos. Meas. Tech.

View full text Add to dashboard Cite

show abstract

“…The photochemistry of pentanedione can be considered in terms of a mechanism which is a modification of that used to describe the photochemistry of biacetyl (16). [41 3Po -+ Product?…”

Section: Resultsmentioning

confidence: 99%

Radiation and Radiationless Processes in 2,3-Pentanedione; Phosphorescence Lifetime in the Gas Phase

Jackson¹,

Yarwood²

1971

Can. J. Chem.

View full text Add to dashboard Cite

Fluorescence and phosphorescence are observed when 2,3-pentanedione in the gaseous state is excited at 365,405, and 436 nm. The phosphorescence lifetime has been investigated as a function of temperature (298 to 363 OK) and concentration of the diketone (0.5 to 90 x M ) . A mechanism that explains the experimental data is proposed. Apart from the radiative process and an intersystem crossing to the ground state, the triplet state 2,3-pentanedione molecules are removed by two other processes. One is a unimolecular reaction with a rate constant of 1 x 10" exp (-ll.O/RT) s-I (consistent with an intramolecular hydrogen atom abstraction), and the other is an interaction with ground state molecules. The photochemistry of the triplet state of 2,3-pentanedione is compared with that of biacetyl to consider the effect of substitution of a hydrogen atom by the methyl group on the radiationless processes in diketones. Many molecules that are of great photochemical interest do not phosphoresce in the gaseous phase, and the presence of triplet states in the system must be deduced in anindirect manner. Two methods that are widely used are the triplet sensitized isomerization of cis-butene-2 introduced by Cundall et al. (1, 2), and the triplet sensitized phosphorescence of biacetyl, first demonstrated by Ishikawa and Noyes (3).The advantages and disadvantages of the techniques have been considered by Noyes and Unger (4). One of the difficulties with biacetyl is the large ratio for emission from the triplet state as compared with that from the singlet state; about 60:l (5) in the direct photolysis at long wavelengths. This implies that the possibility of singlet-singlet energy transfer (with subsequent phosphorescence) must be carefully considered in the system. A further complexity in the biacetyl photolysis is a product which can quench the triplet states very efficiently (6,7); e.g. in the time required to scan the emission from biacetyl as a function of wavelength (excitation source a 1000 W Hg/Xe lamp with a 0.25 m monochromator), an appreciable decrease can occur in the intensity of the phosphorescence and in the lifetime of the triplet biacetyl.The research of Richtol and Klappmeier (8) on 2,3-pentanedione in a matrix at 77 OK and in solution at 298 OK suggests that in the gaseous phase the ratio of phosphorescence to fluorescence would be smaller than for biacetyl. 2,3-Pentanedione might also be less sensitive to the quenching product and it could be an appropriate alternative to biacetyl in energy transfer studies. We have investigated the photochemistry of 2,3-pentanedione at temperatures between 298 and 363 OK and the pre-exponential factors and Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.214.222.130 on 05/10/18For personal use only.

show abstract

“…2, 3, 7, 8, 9, 10, 1 1 could well replace those given by Herr and Noyes (6). These latter have been republished in so many monographs (30,31) and reviews (32,33) that they have gained an authority never claimed by the authors (who suggested their quantum yields were accurate to +-10%). Only Fig.…”

Section: Discussionmentioning

confidence: 91%

The stationary-state approximation in the photolysis of acetone

Nicholson¹

1983

Can. J. Chem.

View full text Add to dashboard Cite

A mechanism has been written for the photolysis of acetone at 313 nm and 253.7 nm and the differential equations involved solved rigorously. Testing this mechanism has revealed inconsistencies between different sets of experiments that were not previously obvious. The stationary-state approximation is valid up to ca. 0.5% decomposition but its practical usefulness is minimal. Graphs are given showing the variation of all significant quantum yields with temperature, pressure, and light intensity.

show abstract

The Primary Photochemical Process In Simple Ketones

Cited by 128 publications

References 78 publications

A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases

A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases

Radiation and Radiationless Processes in 2,3-Pentanedione; Phosphorescence Lifetime in the Gas Phase

The stationary-state approximation in the photolysis of acetone

Contact Info

Product

Resources

About