Formation and stabilization of C6− by radiative electron attachment

Vijayanand Chandrasekaran, Aneesh Prabhakaran, Bhim Kafle, Hilel Rubinstein, Oded Heber, Michael Rappaport, Yoni Toker, Daniel Zajfman

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Radiative electron attachment (REA) plays an important role in forming molecular anions in various astrophysical environments. In this work, we determined the rate coefficient for the formation of C6− by REA based on a detailed balance approach. C6− ions are stored in an electrostatic ion beam trap and are photoexcited above their adiabatic detachment energy (4.18 eV). Due to fast internal conversion and intramolecular vibrational redistribution, photoexcitation leads to the formation of temporary negative ions (TNIs), the same as those one formed by the electron attachment. Absolute vibrational autodetachment and recurrent (or Poincaré) fluorescence (RF) rate coefficients have already been reported [V. Chandrasekaran et al., J. Phys. Chem. Lett. 5, 4078 (2014)]. Knowing the branching ratios of the various competing rate coefficients is decisive to the understanding of the formation probability of anions via REA. The radiative stabilization rate of C6−, shown to be dominated by RF, was determined to be 5 × 104 s−1 at the electron detachment energy, i.e., at least a factor of 100 faster than the stabilization by infrared transitions. The RF is found to very effectively stabilize the TNI formed by electron attachment. Using detailed balance to link the measured delayed detachment rate to the rate of electron attachment, we estimate the REA rate leading to the formation of C6− to be 3 × 10−7 cm3 s−1 at 300 K in agreement with theory (1.7 × 10−7 cm3 s−1 [R. Terzieva and E. Herbst, Int. J. Mass Spectrom. 201, 135 (2000)]). Such a high rate for REA to C6 indicates that REA may play a prominent role in the formation of anions in the interstellar medium.

Original languageEnglish
Article number094302
JournalJournal of Chemical Physics
Issue number9
StatePublished - 7 Mar 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2017 Author(s).


This research was supported by the Israel Science Foundation (Grant No. 1242/09) and by the Benoziyo Endowment Fund for the Advancement of Science. We would like to acknowledge the key contribution to this paper by the late Professor Dirk Schwalm who passed away on July 14, 2016 while this work was in its final stages.

FundersFunder number
Benoziyo Endowment Fund for the Advancement of Science
Israel Science Foundation1242/09


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