Photoabsorption and photoionization of propyne

Abstract

This work measured the absolute photoabsorption cross section of propyne (methylacetylene, CH3CCH) in the 6–30 eV energy range. The valence-shell oscillator strength of 16.97 and the static dipole polarizability of 35.82 atomic units (5.31 Å3) were also derived from the photoabsorption spectrum by the sum-rule method. In the photoionization measurement, the first ionization energy 10.369±0.007 eV of propyne and appearance energies for ion fragments were determined. In addition, new vibrational ν9 and ν10 progressions associated with the X 2E ion state of propyne and Rydberg transitions converged to the A 2E ion state were identified. In addition to the main ν3 progression with the vibrational interval of 1979±39 cm−1, the ν9 and ν10 vibrational structures of the X 2E ion state were resolved with vibrational frequencies of 586±74 cm−1 and 289±65 cm−1, respectively. Moreover, the absolute branching ratios, photoionization quantum yield, and partial photoionization cross sections for C3H4+, C3H3+, C3H2+, and C3H+ production in the 10.3–21.4 eV region were determined. Four shape resonance states were tentatively assigned at 11.2, 12.7, 14.8 and 15.8, and 16.7 eV. Furthermore, a CD3CCH isotopic measurement was taken to examine the reaction pathways of H-dissociative photoionization of propyne. According to the evolution of the C3D3+/C3D2H+ ratio, plausible decay mechanisms for H-dissociative photoionization of propyne were proposed.

Combustion chemistry of the propanol isomers — investigated by electron ionization and VUV-photoionization molecular-beam mass spectrometry

“…The ionization cross sections for both species are taken from [41][42][43]. The summed mole fractions of both isomers from the PI measurements agree well with the mole fraction profiles of C 3 H 4 obtained in the EI measurements.…”

Photoionization mass spectrometric studies and modeling of fuel-rich allene and propyne flames

“…At a photon energy of 10.25 eV, which is above the ionization energy of allene (9.69 eV) [19] and below the ionization energy of propyne (10.36 eV) [20], the m/z = 40 signal consists mostly of allene. The propyne profiles are recorded at 11.1 eV and contributions from the allene isomer are subtracted taking known photoionization efficiencies into account [17,18]. Photoionization cross sections used in this work are given in Refs.…”

“…16.65 eV are not present in the postflame zones and are taken into account using the known gas compositions at the burner surface and the absolute photoionization cross sections of allene/propyne and Ar. [17,18] Diffusion of Ar atoms from the shroud gas into the flames is corrected by assuming a constant Ar signal after reaching its minimum value near 5 mm distance from the burner. The mole fraction profiles for the major species H 2 O, CO, O 2 , and CO 2 are measured at 14.1 eV; the H 2 profiles are recorded at 16.65 eV.…”

Photochemistry of C3Hphydrocarbons in Titan’s stratosphere revisited

“…The photoabsorption cross sections of CH 3 C 2 H and CH 2 CCH 2 are well known (Ho et al 1998;Chen et al 2000). Photolysis studies of these molecules have been performed at 193 nm (Seki & Okabe 1992;Ni et al 1999) and at 155 nm (Harich et al 2000a,b).…”