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

The coupled motion of ions in a radiofrequency trap has been used to connect the frequency-dependent laserinduced heating of a sympathetically cooled spectroscopy ion with changes in the fluorescence of a laser-cooled control ion. This technique, sympathetic heating spectroscopy, is demonstrated using two isotopes of calcium. In the experiment, a few scattered photons from the spectroscopy ion are transformed into a large deviation from the steady-state fluorescence of the control ion. This allows us to detect an optical transition where the number of scattered photons is below our fluorescence detection limit. Possible applications of the technique to molecular ion spectroscopy are briefly discussed.

Escalation of drug self-administration is a consequence of extended drug access and is thought to be specifically related to addiction, but few studies have investigated whether intake of non-drug reinforcers may also escalate with extended-access. The goal of these studies was to determine the effects of limited and extended-access to food reinforcers on behavioral and pharmacological endpoints in mice. In distinct groups, responding on a lever was maintained by liquid reinforcement, or nose-poke responses were maintained by sucrose pellets or liquid food in sessions lasting 1 hour (limited-access) or 10 hours (extended-access). The reinforcing strength of each food, as well as reinforcer-associated cues, was tested before and after extended-access using a progressive ratio (PR) schedule, and locomotor activity in response to novelty and increasing doses of cocaine was assessed in an open field setting in all animals after access to food reinforcers. Escalation of lever-pressing behavior reinforced by liquid food, but not nose-poke behavior reinforced by liquid food or sucrose pellets, was observed across successive extended-access sessions. A concomitant increase in the reinforcing strength of liquid food and its associated cues was apparent in mice that escalated their responding, but not in mice that did not escalate. Finally, extended reinforcer access leading to behavioral escalation was accompanied by an increased sensitivity to the psychostimulant effects of cocaine compared to limited-access. These findings indicate that behavioral escalation can develop as a consequence of extended-access to a non-drug reinforcer, although both the nature of the reinforcer (liquid versus solid food) and the topography of the operant response (lever versus nose-poke) modulate its development. These data also suggest that some of the behavioral and pharmacological corrolaries of behavioral escalation observed following extended-access to drug self-administration may not be due to drug exposure, but rather, may result from basic behavioral processes which underlie operant responding maintained by appetitive stimuli.

The masses of single molecular ions are nondestructively measured by cotrapping the ion of interest with a laser-cooled atomic ion, (40)Ca(+). Measurement of the resolved sidebands of a dipole forbidden transition on the atomic ion reveals the normal-mode frequencies of the two ion system. The mass of two molecular ions, (40)CaH(+) and (40)Ca(16)O(+), are then determined from the normal-mode frequencies. Isotopes of Ca(+) are used to determine the effects of stray electric fields on the normal mode measurement. The future use of resolved sideband experiments for molecular spectroscopy is also discussed.