We demonstrate sympathetic sideband cooling of a 40 CaH + molecular ion co-trapped with a 40 Ca + atomic ion in a linear Paul trap. Both axial modes of the two-ion chain are simultaneously cooled to near the ground state of motion. The center of mass mode is cooled to an average quanta of harmonic motion = ± n 0.13 0.03 COM

We report the measurement of the 1 1 Σ −→ 2 1 Σ transition of CaH + by resonance-enhanced photodissociation of CaH + that is co-trapped with laser-cooled Ca + . We observe four resonances that we assign to transitions from the vibrational v=0 ground state to the v =1-4 excited states based on theoretical predictions. A simple theoretical model that assumes instantaneous dissociation after resonant excitation yield results in good agreement with the observed spectral features except for the unobserved v =0 peak. The resolution of our experiment is limited by the mode-locked excitation laser, but this survey spectroscopy enables future rotationally resolved studies with applications in astrochemistry and precision measurement. 1

We observe vibronic transitions in CaD + between the 1 1 Σ and 2 1 Σ electronic states by resonance enhanced multiphoton photodissociation spectroscopy in a Coulomb crystal. The vibronic transitions are compared with previous measurements on CaH + . The result is a revised assignment of the CaH + vibronic levels and a disagreement with CASPT2 theoretical calculations by approximately 700 cm −1 .

We measure the rovibronic transitions X Σ, v″ = 0, J″ → A Σ, v' = 0-3, J' of CaH and obtain rotational constants for the A Σ state. The spectrum is obtained using two-photon photodissociation of CaH cotrapped with Doppler cooled Ca. The excitation is driven by a mode-locked, frequency-doubled Ti:Sapph laser, which is then pulse shaped to narrow the spectral bandwidth. The measured values of the rotational constants are in agreement with ab initio theory.

Recent high-resolution spectroscopic studies by Merritt, Bondybey, and Heaven (Science 2009, 324, 1548) have heightened the anticipation that small beryllium clusters will soon be observed in the laboratory. Beryllium clusters are important discrete models for the theoretical study of metals. The trigonal bipyramidal Be(5) molecule is studied using high-level coupled cluster methods. We obtain the optimized geometry, atomization and dissociation energies, and vibrational frequencies. The c~CCSDT(Q) method is employed to compute the atomization and dissociation energies. In this approach, complete basis set (CBS) extrapolations at the CCSD(T) level of theory are combined with an additive correction for the effect of iterative triple and perturbative quadruple excitations. Harmonic vibrational frequencies are obtained using analytic gradients computed at the CCSD(T) level of theory. We report an atomization energy of 129.6 kcal mol(-1) at the trigonal bipyramid global minimum geometry. The Be(5)→Be(4)+Be dissociation energy is predicted to be 39.5 kcal mol(-1). The analogous dissociation energies for the smaller beryllium clusters are 64.0 kcal mol(-1) (Be(4)→Be(3)+Be), 24.2 kcal mol(-1) (Be(3)→Be(2)+Be), and 2.7 kcal mol(-1) (Be(2)→Be+Be). The trigonal bipyramidal Be(5) structure has an equatorial-equatorial bond length of 2.000 Å and an axial-equatorial distance of 2.060 Å. Harmonic frequencies of 730, 611, 456, 583, 488, and 338 cm(-1) are obtained at the CCSD(T)/cc-pCVQZ level of theory. Quadruple excitations are found to make noticeable contributions to the energetics of the pentamer, which exhibits a significant level of static correlation.