Photo-dissociation of naphthalene dimer cations stored in a compact electrostatic ion storage ring.

Naphthalene dimer cations [C10H8]2 + have been produced by using an electron cyclotron resonance plasma ion source and stored in a compact electrostatic ion storage ring. We show that the radiative cooling of these cations is much slower than the isolated monomer naphthalene cations. We also report on photo-dissociation studies in the gas phase of naphthalene dimer cations at high internal energy. The dissociation energy is estimated to 0.5 eV in close agreement with previous measurements but a factor of 2 smaller than recent (density functional theory (DFT) and ab initio) theoretical studies. As uncertainties on theory as well as on the experiment cannot be as large as this difference, we conclude that this discrepancy may be due to temperature effects with possible isomerization. As an interpretation of the photo-dissociation spectrum of naphthalene dimer cations, we propose a tentative simple analytical model based on effective Morse potentials. These effective potentials are expected to "average" temperature effects that would apparently result in a smaller energy difference between the fundamental and dissociation states due to the twisting vibration modes of the naphthalene dimer cations.

Polarizability of KC60: evidence for potassium skating on the C60 surface

We present the first measurement of the polarizability and the permanent dipole moment of isolated KC60 molecules by molecular beam deflection technique. We have obtained a value of 2506+/-250 A(3) for the polarizability at room temperature. The addition of a potassium atom enhances by more than a factor of 20 the polarizability of a pure C60 molecule. This very high polarizability and the lack of observed permanent dipole show that the apparent polarizability of KC60 is induced by the free skating of the potassium atom on the C60 surface, resulting in a statistical orientation of the dipole. The results are interpreted with a simple model similar to the Langevin theory for paramagnetic systems.

Theoretical Study of the Electronic Structure of the KRb Molecule.

Upon request of experimentalists now engaged in high-resolution spectroscopic investigations of the molecule KRb, we have determined the potential energy of electronic states (2S+1)Lambda((+)) correlating up to the limit K(5p) + Rb(5s) and of electronic states Omega((+/-)) correlating up to the limit K(4s) + Rb(4d(2)D(3/2)) in a large range of internuclear distance R. For the five states so far observed, the agreement between calculated and experimental molecular constants is good with DeltaR(e) < 0.08 Å, Deltaomega(e) < 6 cm(-1), and DeltaT(e) < 140 cm(-1). Extensive numerical data for energies versus R have been listed in a data base available at http://www.idealibrary.com. Copyright 2000 Academic Press.