Photoabsorption and Photoionization Cross Sections of Pyridine in the Vacuum-Ultraviolet Energy Range

Abstract

We have performed an experimental investigation into the interaction of vacuum-ultraviolet synchrotron radiation with pyridine molecules in the gas phase. Specifically, a double-ion chamber spectrometer was used to measure the absolute photoabsorption cross sections and the photoionization quantum yields from the ionization threshold to 21.5 eV. Moreover, photoionization and neutral-decay cross sections in absolute scale were derived from these data. In addition, the fragmentation pattern was investigated as a function of the photon energy by using a time-of-flight mass spectrometer and the photoelectron-photoion coincidence technique. Thus, the absolute partial ionization cross sections for each ionic fragment were obtained. Comparisons are made with experimental data available in the literature.

Cross Sections and Asymmetry Parameters for Formic Acid in the Vacuum-Ultraviolet Energy Range

“…This methodology enables us to perform measurements only above the first ionization threshold. The experimental setup and procedure have been already described in previous works − and will be briefly presented here. The photoabsorption cross section (σ a ) as a function of photon energy ( E ) is given by where i 1 and i 2 are the ion currents detected using two ion collectors of the same length ( l ) and n is the molecular number density.…”

“…The experimental setup and procedure have been already described in previous works − and will be briefly presented here. The photoabsorption cross section (σ a ) as a function of photon energy ( E ) is given by where i 1 and i 2 are the ion currents detected using two ion collectors of the same length ( l ) and n is the molecular number density. The ion currents were simultaneously recorded by two independent picoammeters (Keithley model 6514) in steps of 0.01 eV.…”

“…The error analysis of the present data was performed following the procedure described by Samson and Yin and also detailed in a previous work of our research group . Random errors, such as fluctuations in ion currents and sample pressure, contribute most significantly to the overall experimental error of the measured data.…”

“…where i 1 and i 2 are the ion currents detected using two ion collectors of the same length (l) 20 and n is the molecular number density. The ion currents were simultaneously recorded by two independent picoammeters (Keithley model 6514) in steps of 0.01 eV.…”

“…The error analysis of the present data was performed following the procedure described by Samson and Yin 14 and also detailed in a previous work of our research group. 20 Random errors, such as fluctuations in ion currents and sample pressure, contribute most significantly to the overall experimental error of the measured data. Statistical fluctuations in the i 1 and i 2 ion current measurements during the energy scans were better than 1 and 2.5% for both Xe and formic acid samples, respectively.…”