Ground and low-lying excited states of propadienylidene (H2C=C=C:) obtained by negative ion photoelectron spectroscopy.


A joint experimental-theoretical study has been carried out on electronic states of propadienylidene (H(2)CCC), using results from negative-ion photoelectron spectroscopy. In addition to the previously characterized X(1)A(1) electronic state, spectroscopic features are observed that belong to five additional states: the low-lying ã(3)B(1) and b(3)A(2) states, as well as two excited singlets, Ã(1)A(2) and B(1)B(1), and a higher-lying triplet, c(3)A(1). Term energies (T(0), in cm(-1)) for the excited states obtained from the data are: 10,354±11 (ã(3)B(1)); 11,950±30 (b(3)A(2)); 20,943±11 (c(3)A(1)); and 13,677±11 (Ã(1)A(2)). Strong vibronic coupling affects the Ã(1)A(2) and B(1)B(1) states as well as ã(3)B(1) and b(3)A(2) and has profound effects on the spectrum. As a result, only a weak, broadened band is observed in the energy region where the origin of the B(1)B(1) state is expected. The assignments here are supported by high-level coupled-cluster calculations and spectral simulations based on a vibronic coupling Hamiltonian. A result of astrophysical interest is that the present study supports the idea that a broad absorption band found at 5450 Å by cavity ringdown spectroscopy (and coincident with a diffuse interstellar band) is carried by the B(1)B(1) state of H(2)CCC.

DOI: 10.1063/1.3696896

Cite this paper

@article{Stanton2012GroundAL, title={Ground and low-lying excited states of propadienylidene (H2C=C=C:) obtained by negative ion photoelectron spectroscopy.}, author={John F Stanton and Etienne Garand and JongJin Kim and Tara I. Yacovitch and Christian Hock and Amanda S Case and Elisa M Miller and Yu-Ju Lu and Kristen M. Vogelhuber and Scott W. Wren and T. Ichino and John P Maier and Robert J. McMahon and David L. Osborn and Daniel M Neumark and W Carl Lineberger}, journal={The Journal of chemical physics}, year={2012}, volume={136 13}, pages={134312} }