Radiative and nonradiative transitions in the first excited singlet state of simple linear aldehydes

Abstract

Nonradiative transitions in the first excited singlet state of perfluorocyclobutanone: Fluorescence decay times and fluorescence excitation spectroscopy Radiative and nonradiative transitions from the first excited singlet state of methylsubstituted naphthalenes Radiative and nonradiative rates of asymmetric linear aldehydes (C 2 -C 6 ) have been measured in the gas phase. Observe radiative lifetimes are compared to calculated radiative lifetimes obtained from the Strickler-Berg (SB) expression. The calculated values are about the same as the observed values in large aldehydes, but the former is about six times greater than the latter in acetaldehyde. The radiative rates are about four orders of magnitude smaller than the nonradiative rates. The two most important nonradiative processes are S\--! T\ intersystem crossing and type II processes, the latter playing an increasingly important role at high energy in the aldehydes with y·hydrogens. The contrasting radiative behavior of the asymmetric aldehydes from that of the symmetrical ketones is intriguing and suggests important differences in their excited state eqUilibrium geometries and transition moments.

Photochemistry of glycolaldehyde in cryogenic matrices

“…The S 1 → S 0 (respectively, T 1 → S 0 ) transitions are predicted around 285 kJ/mol, i.e., near 420 nm (respectively, around 177 kJ/mol, ∼676 nm), in the typical range of fluorescence spectra of many aldehydes. 17 Note that the values found for S 1 -minCC, minTT, or minTG (from 282 to 290 kJ/mol, 413-424 nm) are very close to the fluorescence band measured in solution by Beeby et al (288 kJ/mol, 415 nm). 15 c. Relaxation pathways.…”

“…Aldehydic compounds easily undergo intersystem crossing (ISC) from S 1 to T 1 upon electronic excitation. 17 This is also the case of GA as estimated by the spin-orbit coupling (23.4 cm −1 ) calculated in Ref. 5 for the structure at the minimum energy on S 1 .…”

Time- and space-resolved quantitative LIF measurements of formaldehyde in a heavy-duty diesel engine

“…aldehydes and ketones [24,25]. This is corroborated by the method derived in Section 4 to extract the total CH 2 O fluorescence from the CH 2 O spectral structure intensity.…”

“…Unfortunately, only data on the absorption spectra below typical cold flame temperatures were found. The absorption and emission spectra of aldehydes and some ketones (symmetrical methyl-substituted acetones) have been recorded by Hansen and Lee [24,25]. They show that these species fluoresce in the same wavelength range as CH 2 O but hardly absorb at 355 nm at room temperature.…”

Photolysis of Acetaldehyde in Air: CH4, CO and CO2Quantum Yields

“…Fluorescence from the excited singlet state occurs with quantum yields of (0.1-1.8) 10 À3 in the wavelength region covered. [43] This contribution is small and can be neglected here. Gandini and Hackett [44] have shown that intersystem crossing S 1 !T 1 * occurs at low pressures of acetaldehyde in the absence of added quenching gas.…”