Article ID Journal Published Year Pages File Type
1194643 International Journal of Mass Spectrometry 2007 8 Pages PDF
Abstract

We employed the crossed molecular beams method to synthesize the 2,4-pentadiynylidyne, C5H (X2Π), and the 2,4-pentadiynyl-1, n-C5H3(X2B1), radicals in situ under single collision conditions via the reactions of tricarbon molecules with acetylene and ethylene, respectively. Time-of-flight spectra of the radicals were recorded at the center-of-mass angles at various mass-to-charge ratios from m/z = 63 (C5H3+) to m/z = 36 (C3+). Integrating these time-of-flight spectra and normalizing them to the most intense peak, intensity ratios of I(m/z = 61):I(m/z = 60):I(m/z = 49):I(m/z = 48):I(m/z = 37):I(m/z = 36) = 0.49 ± 0.04:0.27 ± 0.03:1:0.15 ± 0.02:0.32 ± 0.03:0.11 ± 0.04 can be extracted for the 2,4-pentadiynylidyne radical. In case of the 2,4-pentadiynyl-1 molecule, we find intensity ratios of I(m/z = 63):I(m/z = 62):I(m/z = 61):I(m/z = 60):I(m/z = 51):I(m/z = 50):I(m/z = 49):I(m/z = 48):I(m/z = 39):I(m/z = 38):I(m/z = 37):I(m/z = 36) = 0.39 ± 0.04:0.50 ± 0.05:0.32 ± 0.03:0.10 ± 0.03:0.03 ± 0.01:1.0:0.24 ± 0.02:0.02 ± 0.01:0.24 ± 0.03:0.65 ± 0.05:0.57 ± 0.05:0.36 ± 0.03 at an electron impact energy of 70 eV. The absolute ionization cross sections of the 2,4-pentadiynylidyne and 2,4-pentadiynyl radicals were estimated to be 8.6 ± 1.7 × 10−16 cm2 and 9.7 ± 1.9 × 10−16 cm2, respectively. Our data can be employed in future space missions to detect the C5H and C5H3 radicals – crucial reaction intermediates in the formation of polycyclic aromatic hydrocarbon molecules – in the atmospheres of hydrocarbon rich planets (Jupiter, Saturn, Uranus, Neptune, Pluto) and their moons (Titan) and also in combustion flames via mass spectrometry coupled with matrix interval arithmetic.

Related Topics
Physical Sciences and Engineering Chemistry Analytical Chemistry
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