Emission from acetone

Excimers have been suggested in several other photochemical processes. The triplet lifetime of o-xylene decreases from 900 nsec at 0.01 M in methylcyclohexane to 13 nsec in 8M solution.50 The inefficiency of the triplet sensitized dimerization of indene has been attributed to formation of an indene excimer.51 The emission from acetone originally52 believed to arise from an excimer has now been shown53 to be the true monomer fluorescence while that attributed to the monomer appears to have been due to an impurity. 

Data obtained from the photoreduction of benzophenone in isopropanol indicates that the quantum yield (for the formation of acetone) is nearly constant using irradiation at several different wavelengths between 366 and 254 mp..16 The quantum yield for phosphorescence emission from the carbonyl n,ir triplet state is independent of exciting wavelength.22 Furthermore, the singlet excitation spectrum for the phosphorescence emission has been found to be very similar (if not identical) to the absorption spectrum.23 There are other examples where irradiation in the region of a given transition has ultimately led to a triplet of a different type.24... 

Baldwin, I.T., Preston, C., Euler, M. and Gorham, D. (1997). Patterns and consequences of benzyl acetone floral emissions from Nicotiana attenuata plants. Journal of Chemical Ecology 23 2327-2343. 

In this connection investigations are to be mentioned in which a mass-spectrometric analysis has been made of neutral radicals, e.g., CHjCO, split off from acetone by u.v. photons in the ordinary range.27-28 In the first a flash lamp has been used and the radicals were ionized as usual by electron impact. In the second the same radical ionized at a field emission electrode. Recently, several alkyl radicals generated by pyrolysis have been studied. Their values of lv and of the photoionization cross sections could be obtained in the mass spectrometer under monochromatic vacuum u.v. irradiation.29... 

Dry air doped with a chemical ionization reagent (such as Cl2 for anions and acetone or NH3 for cations) sweeps the vapor through a tube containing 10 millicuries of 63Ni. Reagent gas ionized by (3-emission from 63Ni reacts with analyte to generate analyte ions. 

In the vapor phase, the emission from excited acetone has been shown to be a mixture of fluorescence and phosphorescence [254]. The estimated lifetime of the excited singlet state is 10 ns, a figure commonly accepted as a reasonable approximation to the excited singlet to triplet (St - TJ transition time in aliphatic ketones. The overlap of the fluorescence and phosphorescence spectra reflects the fact that the energetic separation between the lowest n, n single and triplet states is small, at least in comparison with the S2 — Tt splitting between lowest excited n, n singlet and triplet states. 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

The oxide-semiconductor-based ethanol sensor is being used to screen intoxicated drivers. In the test condition on the road, the ambient concentrations of CO and N02 can be up to 100 and lOppm due to the emissions from gasoline and diesel engines, respectively.61 The results shown in Fig. 12.6 suggest that the present sensors may be applied for selective detection of ethanol. Acetone is a very rare component in an ordinary ambient atmosphere. However, the expiration of a diabetes patient can contain acetone.62 Acetone concentration in breath air can reach up to 300 ppm in the case of an aceto-acidotic coma related to diabetes mellitus.63,64 This might interfere the ethanol sensor. A high selectivity to ethanol is required for such applications. The SZ sensor at 300°C and the ZW sensor at 400°C can satisfy these requirements. On the contrary, to examine the health condition of a diabetes patient, selective detection of acetone without the interference with alcohol is desirable. In this case, the W sensor at 400°C will be of advantageous. 

Recent studies revealed that, in addition to aldehydes in such systems, there may also exist terpenes, ketones, acetone and hexanal [42-44]. This finding has initiated a growing interest for other possible non-formaldehyde based VOC emissions from wood and wood products. 

EE and PIE from pulling adhesive tape from solid surfaces, measured in vacuum is significantly different from the phE in air. We surveyed the charged particle emission from the peeling of 3M Magic Transparent Tape from a number of surfaces. The surface preparation consisted only of cleaning in acetone - no attempt was made to remove natural oxide layers or other contaminants that would not be removed with acetone. The surface area created by peeling 2... 

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