Efficient creation of molecules from a cesium Bose-Einstein condensate

We report a new scheme to create weakly bound Cs$_2$ molecules from an atomic Bose-Einstein condensate. The method is based on switching the magnetic field to a narrow Feshbach resonance and yields a high atom-molecule conversion efficiency of more than 30%, a factor of three higher than obtained with conventional magnetic-field ramps. The Cs$_2$ molecules are created in a single $g$-wave rotational quantum state. The observed dependence of the conversion efficiency on the magnetic field and atom density shows scattering processes beyond two-body coupling to occur in the vicinity of the Feshbach resonance.Comment: 7 pages, 4 figures, submitted to Europhysics Letter

Metastable Feshbach Molecules in High Rotational States

We experimentally demonstrate Cs2 Feshbach molecules well above the dissociation threshold, which are stable against spontaneous decay on the timescale of one second. An optically trapped sample of ultracold dimers is prepared in an l-wave state and magnetically tuned into a region with negative binding energy. The metastable character of these molecules arises from the large centrifugal barrier in combination with negligible coupling to states with low rotational angular momentum. A sharp onset of dissociation with increasing magnetic field is mediated by a crossing with a g-wave dimer state and facilitates dissociation on demand with a well defined energy.Comment: 4 pages, 5 figure

Observation of Feshbach-like resonances in collisions between ultracold molecules

We observe magnetically tuned collision resonances for ultracold Cs2 molecules stored in a CO2-laser trap. By magnetically levitating the molecules against gravity, we precisely measure their magnetic moment. We find an avoided level crossing which allows us to transfer the molecules into another state. In the new state, two Feshbach-like collision resonances show up as strong inelastic loss features. We interpret these resonances as being induced by Cs4 bound states near the molecular scattering continuum. The tunability of the interactions between molecules opens up novel applications such as controlled chemical reactions and synthesis of ultracold complex molecules

Effect of Greenhouse Temperature on Tomato Yield and Ripening

High fuel costs have encouraged producers of greenhouse tomato (Solanum lycopersicum L.) in the mid-Atlantic region to reduce air temperatures during the day. However, effects on fruit ripening and yield are not known, especially under the low light conditions found in off-season production. This 2-yr study compared fruit ripening and yield of tomato under two temperature regimes during the fall season. Two sets of 18 tomato plants, three rows of six, were grown in soilless culture under either a warm or cool temperature regime. Temperatures were similar during night hours but allowed to rise to at least 21- 24 degrees C in the cool greenhouse section and 23-26 degrees C in the warm section, depending on daily solar heating. Mean 24 hour temperature difference between zones was less than 2 degrees C. Ripe tomato fruit were harvested and weighed 3 times per week for 8 weeks and the remaining un-ripened green tomatoes were weighed at the termination of the experiment to obtain total fruit biomass. The warm zone produced significantly greater weight of ripe tomatoes (23%) than the cool zone. However, total fruit weight (ripe and green), was not significantly different. Thus a relatively small increase in temperature (2 degrees C) during the mid-day was associated with a significant increase in fruit ripening but not in total fruit weight. This study showed that greenhouse temperature could be used to better manage fruit production to match weekly market demand without affecting total fruit weight and that consistently maintaining a cool greenhouse would delay tomato ripening and likely increase the potential for plant stress due to high fruit loads remaining on the vines

Experimental Evidence for Efimov Quantum States

Three interacting particles form a system which is well known for its complex physical behavior. A landmark theoretical result in few-body quantum physics is Efimov's prediction of a universal set of weakly bound trimer states appearing for three identical bosons with a resonant two-body interaction. Surprisingly, these states even exist in the absence of a corresponding two-body bound state and their precise nature is largely independent of the particular type of the two-body interaction potential. Efimov's scenario has attracted great interest in many areas of physics; an experimental test however has not been achieved. We report the observation of an Efimov resonance in an ultracold thermal gas of cesium atoms. The resonance occurs in the range of large negative two-body scattering lengths and arises from the coupling of three free atoms to an Efimov trimer. We observe its signature as a giant three-body recombination loss when the strength of the two-body interaction is varied near a Feshbach resonance. This resonance develops into a continuum resonance at non-zero collision energies, and we observe a shift of the resonance position as a function of temperature. We also report on a minimum in the recombination loss for positive scattering lengths, indicating destructive interference of decay pathways. Our results confirm central theoretical predictions of Efimov physics and represent a starting point from which to explore the universal properties of resonantly interacting few-body systems.Comment: 8 pages, 4 figures, Proceedings of ICAP-2006 (Innsbruck

`St\"uckelberg interferometry' with ultracold molecules

We report on the realization of a time-domain `St\"uckelberg interferometer', which is based on the internal state structure of ultracold Feshbach molecules. Two subsequent passages through a weak avoided crossing between two different orbital angular momentum states in combination with a variable hold time lead to high-contrast population oscillations. This allows for a precise determination of the energy difference between the two molecular states. We demonstrate a high degree of control over the interferometer dynamics. The interferometric scheme provides new possibilities for precision measurements with ultracold molecules.Comment: 4 pages, 5 figure

Spectroscopy of Ultracold, Trapped Cesium Feshbach Molecules

We explore the rich internal structure of Cs_2 Feshbach molecules. Pure ultracold molecular samples are prepared in a CO_2-laser trap, and a multitude of weakly bound states is populated by elaborate magnetic-field ramping techniques. Our methods use different Feshbach resonances as input ports and various internal level crossings for controlled state transfer. We populate higher partial-wave states of up to eight units of rotational angular momentum (l-wave states). We investigate the molecular structure by measurements of the magnetic moments for various states. Avoided level crossings between different molecular states are characterized through the changes in magnetic moment and by a Landau-Zener tunneling method. Based on microwave spectroscopy, we present a precise measurement of the magnetic-field dependent binding energy of the weakly bound s-wave state that is responsible for the large background scattering length of Cs. This state is of particular interest because of its quantum-halo character.Comment: 15 pages, 12 figures, 4 table

Comparison of the ramp versus standard exercise protocols

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test.Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 ± 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 ± 7 ml/kg per min) (< 0.01), although no differences were observed in maximal heart rate (131 ± 24 versus 126 ± 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope ± SEE ml/kg per min = 0.80 ± 2.5 and 0.78 ±1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 ± 4.0 and 0.59 ± 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).Normal subjects demonstrated a greater slope (0.71 ± 4.2) than did patients with chronic heart failure (0.53 ± 2.8), coronary artery disease (0.51 ± 2.6) and angina (0.53 ± 3.1) (< 0.001). The difference between measured and predicted maximal oxygen uptake was greatest for the tests with the largest increments between stages (>1 metabolic equivalent (MET) for the Bruce treadmill and 50 W/stage cycle ergometer) and least for the tests with the smallest increments between stages (ramp tests and 25 W/stage cycle ergometer). These findings suggest that the exercise protocol, even when the same mode is used, can result in marked variations in maximal oxygen uptake and the dynamics of gas exchange during exercise testing

Evidence for Efimov quantum states in an ultracold gas of cesium atoms

Systems of three interacting particles are notorious for their complex physical behavior. A landmark theoretical result in few-body quantum physics is Efimov's prediction of a universal set of bound trimer states appearing for three identical bosons with a resonant two-body interaction. Counterintuitively, these states even exist in the absence of a corresponding two-body bound state. Since the formulation of Efimov's problem in the context of nuclear physics 35 years ago, it has attracted great interest in many areas of physics. However, the observation of Efimov quantum states has remained an elusive goal. Here we report the observation of an Efimov resonance in an ultracold gas of cesium atoms. The resonance occurs in the range of large negative two-body scattering lengths, arising from the coupling of three free atoms to an Efimov trimer. Experimentally, we observe its signature as a giant three-body recombination loss when the strength of the two-body interaction is varied. We also detect a minimum in the recombination loss for positive scattering lengths, indicating destructive interference of decay pathways. Our results confirm central theoretical predictions of Efimov physics and represent a starting point with which to explore the universal properties of resonantly interacting few-body systems. While Feshbach resonances have provided the key to control quantum-mechanical interactions on the two-body level, Efimov resonances connect ultracold matter to the world of few-body quantum phenomena.Comment: 18 pages, 3 figure