Volume 130, Issue 5, 07 February 2009
Index of content:
130(2009); http://dx.doi.org/10.1063/1.3073884View Description Hide Description
The golden cage is doped systematically with an external atom of different valence electrons:Ag,Zn, and In. The electronic and structural properties of the doped clusters, , are investigated by photoelectron spectroscopy and theoretical calculations. It is observed that the characteristic spectral features of , reflecting its near tetrahedral symmetry, are retained in the photoelectron spectra of , suggesting endohedral structures with little distortion from the parent cage for the doped clusters. Density functional calculations show that the endohedral structures of with symmetry are low-lying structures, which give simulated photoelectron spectra in good agreement with the experiment. It is found that the dopant atom does not significantly perturb the electronic and atomic structures of , but simply donate its valence electrons to the parent cage, resulting in a closed-shell 18-electron system for , a 19-electron system for with a large energy gap, and a 20-electron system for . The current work shows that the electronic properties of the golden buckyball can be systematically tuned through doping.
Experimental investigation of the triplet ground state: Multiparameter Morse long range potential analysis and molecular constants130(2009); http://dx.doi.org/10.1063/1.3075580View Description Hide Description
We have observed the vibrational levels of the state by perturbation facilitated infrared-infrared double resonance excitation and spectrally resolved fluorescence measurements, and derived a multiparameter Morse long range potential and molecular constants based on these data.
Force spectroscopy of a single artificial biomolecule bond: The Kramers’ high-barrier limit holds close to the critical force130(2009); http://dx.doi.org/10.1063/1.3077010View Description Hide Description
We use a minimal system with a single micron-size bead trapped with optical tweezers to investigate the kinetics of escape under force. Surprisingly, the exponential decay of the off rate with the barrier energy is still valid close to the critical force. Hence, the high viscosity approximation derived by Kramers in the case of a high energy barrier holds even for an energy barrier close to the thermal energy. Several recent models describe a single biomoleculebond by a smooth single-barrier energy profile. When this approach is accurate enough, our result justifies the use of Kramers’ approximation in the high-force regime, close to the critical force of the system, as done in recent single biomoleculebond studies.