Branching ratios for the dissociative recombination of hydrocarbon ions. I: The cases of C4H9+ and C4H5+

Modeling the ortho-to-para abundance ratio of cyclic C3H2in cold dense cores

“…Note that this ion has three-fold symmetry so that its protons are all indistinguishable: the ortho form has a total nuclear spin of 3/2, while the two para forms (Oka 2004) each have a total nuclear spin of 1/2, although only one of these exists for a given rotational state (Townes & Schawlow 1975). Secondly, we added new experimental information on the neutral products and total rate coefficients for dissociative recombination reactions involving several hydrocarbon ions Semaniak et al 1998;Kalhori et al 2002;Derkatch et al 1999;Mitchell et al 2003). Thirdly, we ignored the existence of the linear isomer of lower abundance -l-C 3 H 2 -to simplify the problem for c-C 3 H 2 .…”

Branching ratios for the dissociative recombination of hydrocarbon ions

“…Thus, the number particles in peaks I-IV being N I , N II , N III and N IV is given by where N 2a , N 2b , N 2c and N 2d are the fractions of the total number of recombinations that yield channels 2a, 2b, 2c and 2d, respectively. This method has been used previously in a large number of branching ratio measurements with hydrocarbon molecular ions at ASTRID [9,11] and also at CRYRING at the Manne Siegbahn Laboratory in Sweden [12][13][14][15][16][17]. A series of equations was presented in [9] that allowed for corrections due to light fragments missing the detector.…”

“…They are also observed in the interstellar environment in interstellar clouds and cometary atmospheres [7]. When starting from simple hydrocarbon precursors, complex ions are produced in a sequence of ion-molecule reactions [8], and are neutralized in the process of dissociative recombination (DR) in which the polyatomic ion collides with an electron and subsequently dissociate into neutral fragments: In a recent experiment [9], we have used the storage ring technique to determine the branching ratios for the dissociative recombination of C 4 H 9 + and C 4 H 5 + ions with low energy electrons. It was found that while C 4 H 9 + dissociated either to form C 4 or C 3 + C products, i.e.…”

Branching ratios for the dissociative recombination of hydrocarbon ions

“…Branching ratios for the dissociative recombination of hydrocarbon ions with the general formula C 2 H + 3 , C 3 H + m (m = 1-8) and C 4 H + m (m = 1-9) have been measured by us using the electron cooler at the ASTRID ion storage ring [8][9][10], shown in figure 1, and full details of the measurement technique have been given in these references.…”

“…If some of the lighter fragments with only a single carbon atom fly apart too far from the primary beam direction and are not counted by the detector, this loss can be taken account of by modifying the above equations [8]. As seen in figure 2, however, there is no indication there of such a loss as differences appear only in peak IV when no grid is used.…”