On the Vertical and Adiabatic Excitation Energies of the 21A(g), State of trans-1,3-butadiene

Authors

Jason Lappe '00, Harvey Mudd College
Robert J. Cave, Harvey Mudd CollegeFollow

Student Co-author

HMC Undergraduate

Document Type

Article

Department

Chemistry (HMC)

Publication Date

2000

Abstract

The excitation energy to the 2¹A_g state of trans-1,3-butadiene is examined using a variety of ab initio electronic structure techniques. While analogous states have been shown to be the lowest singlet excited states for all longer polyenes, for butadiene the position of the 2¹A_g state relative to the HOMO → LUMO excitation (1¹B_u) has been difficult to establish theoretically. We employ a variety of methods (CASSCF, CASPT2, MRSDCI, QDVPT) to examine both the vertical and adiabatic excitation energies for this state. At the ground-state geometry, the vertical excitation energies obtained by CASPT2 and Davidson-corrected MRSDCI for the 2¹A_g state differ by approximately 0.15 eV, but all of the methods predict that the 2¹A_g state has a lower 0−0 excitation energy than the 1¹B_u state. Possible reasons for the discrepancies between the various methods for the vertical excitation energy are discussed.

Rights Information

© 2000 American Chemical Society

DOI

10.1021/jp992518z

Recommended Citation

Lappe, J.; Cave, R.J. “On the Vertical and Adiabatic Excitation Energies of the 21A(g), State of trans-1,3-butadiene,” J. Phys. Chem. A 2000, 104, 22294. DOI: 10.1021/jp992518z