Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session H24: Focus Session: Production and Application of Cold Molecules I |
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Sponsoring Units: DCP Chair: David Chandler, Sandia National Laboratories Room: D133-D134 |
Tuesday, March 16, 2010 8:00AM - 8:36AM |
H24.00001: Cold, Trapped Molecules via Cryogenic Buffer Gas Methods Invited Speaker: We present a summary of recent results from our group on the cooling of molecules using cryogenic buffer-gas techniques. A variety of molecules are cooled, including NH, NH$_3$, O$_2$, ThO and Naphthalene. NH is magnetically trapped and studied for times longer than 10 seconds. Spin relaxation cross-sections (in-trap) are measured. NH is co-trapped with atomic nitrogen (N). Preliminary results for both theoretical and experimental N-NH collisional properties will be presented. Cold molecular beams of unprecedented flux are demonstrated with a wide variety of species, including ThO, as well as with atomic species. These sources can form the basis for new precision tests as well as for further work towards (co-)trapping and cooling of atoms and molecules. We also briefly describe our creation of BEC in the atomic species He* using buffer-gas methods, without laser cooling. A summary of possible future directions will be presented. [Preview Abstract] |
Tuesday, March 16, 2010 8:36AM - 8:48AM |
H24.00002: Femtosecond time-resolved EUV photoion imaging studies of pure helium nanodroplets Oliver Buenermann, Oleg Kornilov, Oliver Gessner, Stephen R. Leone, Daniel M. Neumark Helium nanodroplets provide a cryogenic, weakly interacting matrix for the isolation and spectroscopy of molecules and clusters. The relaxation dynamics of electronically excited helium nanodroplets are investigated by femtosecond time resolved photoion imaging studies. The droplets are excited into a broad absorption band centered at 23.8 eV. The electronic and nuclear dynamics following this excitation are monitored by photoionization with a 785nm probe pulse. A Wiley-McLaren time of flight spectrometer equipped with a time- and position sensitive delay line detector facilitates the measurement of mass selective ion kinetic energy distributions. First measurements reveal differences in the kinetic energy release of the Helium monomer, dimer and trimer ions. Furthermore, the pump-probe time-delay dependent ion spectra exhibit several features evolving on various timescales. The combination of these results with previously recorded photoelectron imaging measurements allows for a new level of insight into the electronic and nuclear dynamics of electronically excited helium nanodroplets. [Preview Abstract] |
Tuesday, March 16, 2010 8:48AM - 9:24AM |
H24.00003: Stark and Zeeman deceleration of atoms and molecules Invited Speaker: In the past years considerable efforts have been invested to develop general methods with which to produce cold samples of atoms and molecules that cannot be laser cooled. Methods developed so far include, among others, the photoassociation of ultracold atoms [1], buffer-gas cooling [2] and multistage Stark deceleration [3]. With the aim of performing high-resolution spectroscopic measurements, we have recently contributed to the development of two new methods of producing cold samples of atoms and molecules starting from supersonic beams: Rydberg-Stark deceleration [4] and multistage Zeeman deceleration [5,6]. The talk will provide a description of these two methods. The former method exploits the very large dipole moments (more than 1000 Debye) that can be induced in atomic and molecular Rydberg states by electric fields and was recently used to stop and trap clouds of translationally cold Rydberg atoms and molecules after deceleration in a single-stage device [7,8]. The latter method exploits the Zeeman effect in paramagnetic species and the ability to switch on and off large magnetic fields ($>$2 Tesla) in about 5 $\mu$s. It was used to decelerate an atomic sample initially in a supersonic beam to zero velocity in the laboratory reference frame and subsequently load the atoms into a magnetic trap [9]. The deceleration methods, the diagnostic methods to characterize the velocity distributions of the decelerated species and the trapping methods will be illustrated by experiments conducted on hydrogen atoms and molecules. \newline \newline [1] A. Fioretti, D. Comparat, A. Crubellier, O. Dulieu, F. Masnou-Seeuws and P. Pillet, Phys. Rev. Lett. 80, 4402 (1998) [2] J. M. Doyle, B. Friedrich, J. Kim and D. Patterson, Phys. Rev. A 52, 2515 (1995) [3] H. L. Bethlem, G. Berden and G. Meijer, Phys. Rev. Lett. 83, 1558 (1999). [4] S. R. Procter, Y. Yamakita, F. Merkt and T. P. Softley, Chem. Phys. Lett. 374, 667 (2003) [5] N. Vanhaecke, U. Meier, M. Andrist, B. H. Meier and F. Merkt, Phys. Rev A 75, 031402(R) (2007) [6] E. Narevicius, A. Libson, C. G. Parthey, I. Chavez, J. Narevicius, U. Even and M. G. Raizen, Phys. Rev. Lett. 100, 093003 (2008) [7] S. D. Hogan and F. Merkt, Phys. Rev. Lett. 100, 043001 (2008) [8] S. D. Hogan, Ch. Seiler and F. Merkt, Phys. Rev. Lett. 103, 123001 (2009) [9] S. D. Hogan, A. W. Wiederkehr, H. Schmutz and F. Merkt, Phys. Rev. Lett. 101, 143001 (2008) [Preview Abstract] |
Tuesday, March 16, 2010 9:24AM - 9:36AM |
H24.00004: Cold dipolar collisions between buffer gas cooled ND$_{3}$ and Stark decelerated OH molecules Brian Sawyer, Benjamin Stuhl, Mark Yeo, David Patterson, John Doyle, Jun Ye There is currently much theoretical and experimental interest in the collisions of neutral polar molecules at cold and ultracold temperatures. The long-range, anisotropic dipole-dipole interaction between such molecules may be exploited to control elastic, inelastic, or even reactive rates in a variable electric field. We employ two direct molecular cooling methods - Stark deceleration and buffer gas cooling - to collide a slow ($\sim$100 m/s) continuous beam of state-selected ND$_{3}$ molecules with a magnetically trapped sample of state-selected OH. The collisions between the two species occur within a permanent magnetic trap at the terminus of a Stark decelerator. The magnetic trap design allows for application of a variable electric field ($<$100 kV/cm) to the collision region to fully polarize both species. We report progress toward observation of electric field dependent elastic and inelastic collision rates at $\sim$1 K. [Preview Abstract] |
Tuesday, March 16, 2010 9:36AM - 10:12AM |
H24.00005: Taming molecular beams; towards a molecular laboratory on a chip Invited Speaker: The motion of neutral molecules in a beam can be manipulated with inhomogeneous electric and magnetic fields. Static fields can be used to deflect or focus molecules, whereas time-varying fields can be used to decelerate or accelerate beams of molecules to any desired velocity. I will give an overview of the possibilities that this molecular beam technology presently offers, ranging from ultrahigh-resolution spectroscopy and novel scattering experiments to lifetime measurements on trapped molecules. I will report in particular on our recent experiments demonstrating trapping of carbon monoxide molecules on a chip using direct loading from a supersonic beam. Upon arrival above the chip, the molecules are confined in tubular electric field traps of about 20 micrometer diameter, centred 25 micrometer above the chip, that move along with the molecular beam at a velocity of several hundred meters per second. By using the 13-C carbon monoxide isotopologue, losses due to nonadiabatic transitions near the center of the tubular traps are prevented. An array of these miniaturized moving traps can be brought to a complete standstill over a distance of only a few centimetres. After a certain holding time, the molecules can be accelerated off the chip again for detection. This loading and detection methodology is applicable to a wide variety of polar molecules, and enables the creation of a molecular laboratory on a chip. Many of the gas phase molecular physics experiments that are currently being performed in large beam machines might be performed in a compact vacuum machine on a surface area of a few square centimetres in the future and new experiments will become possible. [Preview Abstract] |
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