K. Yokoyama et al., AUTODETACHMENT SPECTROSCOPY AND DYNAMICS OF DIPOLE BOUND-STATES OF NEGATIVE-IONS - (2)A(1)-B-2(1) TRANSITIONS OF H2CCC-, The Journal of chemical physics, 105(24), 1996, pp. 10696-10705
The H2CCC- ion is studied by autodetachment spectroscopy in a coaxial
laser-ion beam spectrometer. Sharp resonances at photon energies near
the photodetachment threshold energy are ascribed to a (2)A(1) <-- B-2
(1) transition followed by autodetachment of the dipole-bound state (D
BS). Some 2500 rotational transitions are assigned and the band origin
is determined to be 14 284.420(5) cm(-1). The observation of individu
al rotational lines allowed determination of the rotational spectrosco
pic constants as A=9.651 53(4) cm(-1) and (B + C)/2=0.346 461(3) cm(-1
) for the DBS as well as the spin-rotation coupling constant epsilon(a
a)=2.17(6)x10(-3) cm(-1). Based on an electron affinity of 14 469+/-64
cm(-1), the binding energy of the electron in the DBS is 170+/-50 cm(
-1). Anomalous rotational line positions are found in the vicinity of
K-a=7-10 in the DBS and have been attributed to the centrifugal distor
tion couplings caused by mixing with the CCC out-of-plane bending mode
(nu(6)) and the CCC in-plane bending mode (nu(9)). The linewidths pro
vide information about autodetachment rates that make it possible to o
btain electron detachment dynamics for individual rotational states. (
C) 1996 American Institute of Physics.