Phys. Rev. A 98, 063434 (2018)

Electronic and vibrational radiative cooling of the small carbon clusters C₄⁻ and C₆⁻

N. Kono^*,1, R. Suzuki¹, T. Furukawa¹, J. Matsumoto¹, H. Tanuma¹, H. Shiromaru¹, T. Azuma², K. Hansen^3,4

1 Faculty of Science, Tokyo Metropolitan University, Hachioji, Tokyo, 192-0397, Japan

2 Atomic, Molecular and Optical Physics Laboratory, RIKEN, Wako, Saitama, 351-0198, Japan

3 Joint Center of Quantum Studies and Department of Physics, Tianjin University, Tianjin 300072, China

4 Department of Physics, Gothenburg University, 41296 Gothenburg, Sweden

* kouno-naoko@ed.tmu.ac.jp

ABSTRACT

Delayed electron detachment yields of ${C_4}^{-}$ and ${C_6}^{-}$ induced by photoexcitation in an electrostatic ion storage ring were measured as functions of excitation energies and laser firing times, allowing for a mapping of their radiative cooling in a wide energy range. The energy window concept and discrimination of one- and two-photon absorption are critical in understanding the obtained results. The experimentally obtained electronic and vibrational cooling rates were consistent with a simulation based on detailed-balance theory. The even-odd alternation of vibrational cooling rates, predicted from IR intensities, was also examined. We found that the larger anion cools faster, with no indication of an even-odd alternation.