TITLE

The S1/S2 exciton interaction in 2-pyridone·6-methyl-2-pyridone: Davydov splitting, vibronic coupling, and vibronic quenching

AUTHOR(S)
Heid, Cornelia G.; Ottiger, Philipp; Leist, Roman; Leutwyler, Samuel
PUB. DATE
October 2011
SOURCE
Journal of Chemical Physics;10/21/2011, Vol. 135 Issue 15, p154311
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The excitonic splitting between the S1 and S2 electronic states of the doubly hydrogen-bonded dimer 2-pyridone·6-methyl-2-pyridone (2PY·6M2PY) is studied in a supersonic jet, applying two-color resonant two-photon ionization (2C-R2PI), UV-UV depletion, and dispersed fluorescence spectroscopies. In contrast to the C2h symmetric (2-pyridone)2 homodimer, in which the S1 ← S0 transition is symmetry-forbidden but the S2 ← S0 transition is allowed, the symmetry-breaking by the additional methyl group in 2PY·6M2PY leads to the appearance of both the S1 and S2 origins, which are separated by Δexp = 154 cm-1. When combined with the separation of the S1 ← S0 excitations of 6M2PY and 2PY, which is δ = 102 cm-1, one obtains an S1/S2 exciton coupling matrix element of VAB, el = 57 cm-1 in a Frenkel-Davydov exciton model. The vibronic couplings in the S1/S2 ← S0 spectrum of 2PY·6M2PY are treated by the Fulton-Gouterman single-mode model. We consider independent couplings to the intramolecular 6a′ vibration and to the intermolecular σ′ stretch, and obtain a semi-quantitative fit to the observed spectrum. The dimensionless excitonic couplings are C(6a′) = 0.15 and C(σ′) = 0.05, which places this dimer in the weak-coupling limit. However, the S1/S2 state exciton splittings Δcalc calculated by the configuration interaction singles method (CIS), time-dependent Hartree-Fock (TD-HF), and approximate second-order coupled-cluster method (CC2) are between 1100 and 1450 cm-1, or seven to nine times larger than observed. These huge errors result from the neglect of the coupling to the optically active intra- and intermolecular vibrations of the dimer, which lead to vibronic quenching of the purely electronic excitonic splitting. For 2PY·6M2PY the electronic splitting is quenched by a factor of ∼30 (i.e., the vibronic quenching factor is Γexp = 0.035), which brings the calculated splittings into close agreement with the experimentally observed value. The 2C-R2PI and fluorescence spectra of the tautomeric species 2-hydroxypyridine·6-methyl-2-pyridone (2HP·6M2PY) are also observed and assigned.
ACCESSION #
66715499

 

Related Articles

  • Finite-element multiconfiguration Hartree–Fock calculations on the excitation energies and the ionization potential of oxygen. Sundholm, Dage; Olsen, Jeppe; Alexander, S. A. // Journal of Chemical Physics;4/1/1992, Vol. 96 Issue 7, p5229 

    The 3P, 1D, and 1S states of oxygen and the 4S ground state of the oxygen cation have been studied using large numerical multiconfiguration Hartree–Fock calculations with systematically increased active spaces. The nonrelativistic valence limits for the excitation energies are 1.968 and...

  • Radiative lifetime and oscillator strength determinations in Xe VI. Biémont, É.; Buchard, V.; Garnir, H.-P.; Lefèbvre, P.-H.; Quinet, P. // European Physical Journal D -- Atoms, Molecules, Clusters & Opti;May2005, Vol. 33 Issue 2, p181 

    Transition probabilities have been calculated for Δn = 0 and Δn = 1 transitions connecting the 5s2nl [ np (n=5-8); nf (n=4-5); nh (n=6-8); nk (n=8)] , 5s5pnl (nl=5d,6s), 5p3 and 5s2nl [ (ns (n=6-8); nd (n=5-8); ng (n=5-6); ni (n=7-8)] and 5s5p2 configurations...

  • Application of an efficient multireference approach to free-base porphin and metalloporphyrins: Ground, excited, and positive ion states. Chaudhuri, Rajat K; Freed, Karl F.; Chattopadhyay, Sudip; Mahapatra, Uttam Sinha // Journal of Chemical Physics;8/28/2011, Vol. 135 Issue 8, p084118 

    The improved virtual orbital-complete active space configuration interaction (IVO-CASCI) method is applied to determine the geometries of the ground state of free-base porphin and its metal derivatives, magnesium and zinc porphyrins. The vertical excitation energies and ionization potentials are...

  • Calculation and interpretation of total energies in electron propagator theory. Ortiz, J. V. // Journal of Chemical Physics;10/1/1995, Vol. 103 Issue 13, p5630 

    Ground state total energies and one-electron density matrices can be calculated from contour integrals over the electron propagator. Ionization energies and corresponding Feynman–Dyson amplitudes are related simply to ground state properties. Total energy formulas derived from electron...

  • Comparison between molecular orbital and surface integral calculations of the exchange energy for the homonuclear dimer ions He+2, Li+2, and Be+2. Chang, T. C.; Tang, K. T. // Journal of Chemical Physics;12/22/1995, Vol. 103 Issue 24, p10580 

    The exchange energy, defined as half of the energy splitting of the gerade and ungerade states of a molecular ion, is investigated by molecular orbital calculations and by the surface integral method. Numerical results of He+2, Li+2, and Be+2 are obtained through restricted Hartree–Fock,...

  • Radial behavior of the average local ionization energies of atoms. Politzer, Peter; Murray, Jane S.; Grice, M. Edward; Brinck, Tore; Ranganathan, Shoba // Journal of Chemical Physics;11/1/1991, Vol. 95 Issue 9, p6699 

    The radial behavior of the average local ionization energy I(r) has been investigated for the atoms He–Kr, using ab initio Hartree–Fock atomic wave functions. I(r) is found to decrease in a stepwise manner with the inflection points serving effectively to define boundaries between...

  • The exactness of the extended Koopmans’ theorem: A numerical study. Sundholm, Dage; Olsen, Jeppe // Journal of Chemical Physics;3/1/1993, Vol. 98 Issue 5, p3999 

    The exactness of the extended Koopmans’ theorem has been studied by comparing multiconfiguration Hartree–Fock calculations on Be(1S) with configuration interaction calculations on Be+(2S) performed in the same basis. The lowest ionization potentials calculated as the energy...

  • A linear combination of Gaussian-type orbitals (LCGTO) Xα study of ferrocene: The metal-to-ring distance and ionization potentials. Rösch, N.; Jörg, H. // Journal of Chemical Physics;5/15/1986, Vol. 84 Issue 10, p5967 

    The metal-to-ring distance of ferrocene, Fe(C5H5)2, has been optimized using the LCGTO-Xα method. The resulting distance is 0.047 Å shorter than the experimental value of 1.65 Å. The corresponding symmetric stretching frequency of 331 cm-1 shows good agreement with experiment (303...

  • Relativistic effects on sixth group monohydrides. Pisani, L.; Clementi, E. // Journal of Chemical Physics;12/1/1995, Vol. 103 Issue 21, p9321 

    Dirac–Fock and Hartree–Fock calculations have been performed for the ground state of the HO, HS, HSe, HTe, and HPo molecules. Equilibrium geometries, atomization energies, and ionization potentials, with both methods, are evaluated, compared, and discussed. Calculations on the...

Share

Read the Article

Courtesy of NEW JERSEY STATE LIBRARY

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics