Determination of fluorescence and non-radiative de-excitation rates of excited 3-pentanone at low pressures

3-Pentanone photophysics measurements and subsequent fluorescence quantum yield (FQY) model development are presented. A heated, flowing optical cell and laser excitation at 248, 266, 277, and 308 nm were utilized, allowing investigation of FQY and absorption cross-section values for 3-pentanone vapor from 298 to 690 K and 10 to 30 mbar. Measurements of FQY were also made for 20 mbar of 3-pentanone at 1.3 bar total pressure in nitrogen from 298 to 530 K and in air from 298 to 487 K. Absolute FQY was determined by calibration to Rayleigh scattering of nitrogen gas. Based on these FQY measurements and fluorescence lifetime data from previous work, the fluorescence rate k _f was determined to be 3.70×10⁵ s⁻¹. The current work extends knowledge of the non-radiative rate k _nr to vibrational energies of 15000 cm⁻¹, and the expression for k _nr was optimized to include a fit to these new data points. Finally, variation of FQY with 3-pentanone vapor pressure was used to optimize the vibrational relaxation cascade parameter α _3p . The updated FQY model for 3-pentanone vapor shows agreement within 8% to the current FQY data across the investigated range of temperatures and pressures.