First-principles simulation of the UV absorption spectrum of ketene

The absorption spectrum of ketene (CH2=C=O) in the 145- to 220-nm region is calculated completely from first principles and compared to a recent high-resolution synchrotron radiation experiment (J Chem Phys 2002, 117, 4306). The simulations are based on a vibronic model, which is extracted from routinely applicable coupled cluster calculations for electronically excited states. Nonadiabatic effects are assessed by a comparison of the vibronic model simulations with Franck-Condon calculations and are found to be important to understand various aspects of the absorption spectrum of ketene. (C) 2003 Wiley Periodicals, Inc.