Mass spectrum of the 1-butene-3-yne-2-yl radical (i-C4H3; X2A′)

The crossed molecular beams method has been applied to produce the 1-butene-3-yne-2-yl radical, i-C4H3(X2A′) under single collision conditions via the reaction of dicarbon molecules with ethylene. We recorded time-of-flight spectra of the radical at the center-of-mass angle (28.0◦) of the parent ion (m/z= 51; C4H3) and of the fragments at m/z= 50 (C4H2), m/z= 49 (C4H), m/z= 48 (C4), m/z= 39 (C3H3), m/z= 38 (C3H2), m/z= 37 (C3H), and m/z= 36 (C3). This yielded relative intensity ratios of 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) = 0.47± 0.01:0.94± 0.01:1.0:0.07± 0.02:0.31± 0.01:0.23± 0.02:0.24± 0.01:0.12± 0.01 at 70 eV electron impact energy. Upper limits at mass-to-charge ratios between 27 and m/z= 24 and m/z= 14–12 were derived to be 0.02± 0.01. Note that the intensity of the 13C isotopic peak of the 1-butene-3-yne-2-yl radical at m/z= 52 (13C12C H +) is about 0.04± 0.01 relative to m/z= 51. E 7 w s ©