Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A3: Invited Session: New Frontiers in Laser Science |
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Sponsoring Units: DLS Chair: Stephen Bradforth, University of Southern California Room: 002AB |
Monday, March 2, 2015 8:00AM - 8:36AM |
A3.00001: Laser driven hydrogen transfer reactions in atmospheric chemistry Invited Speaker: Marsha I. Lester Ozonolysis of alkenes, an important non-photolytic source of OH radicals in the troposphere, proceeds through energized Criegee intermediates that undergo unimolecular decay to produce OH radicals. In this work, infrared laser activation of cold methyl-substituted Criegee intermediates is utilized to drive hydrogen transfer from the methyl group to the terminal oxygen, followed by dissociation to OH radicals. State-selective excitation of the Criegee intermediates in the CH stretch overtone region combined with sensitive OH detection reveals the infrared spectra of CH$_{3}$CHOO and (CH$_{3})_{2}$COO, effective barrier heights for the critical hydrogen transfer step, and rapid decay dynamics to OH products. Complementary theory provides insights on the infrared overtone spectra as well as vibrational excitations, structural changes, and energy required to move from the minimum energy configuration of the Criegee intermediates to the transition state for the hydrogen transfer reaction. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 9:12AM |
A3.00002: Remote Detection via Quantum Coherence Invited Speaker: Marlan Scully There is nothing so practical as basic science. As a case in point, the compelling need for standoff detection of hazardous gases and vapor indicators of explosives has motivated the development of remotely pumped, scheme(s) which produce radiation in the backward direction [Science, 331(6016), 442-445 (2011); PRX, 3, 041001 (2013)]. Moving from conceptualization to theoretical analysis and experimental verification, we demonstrate that high gain can be achieved in air. Backward air lasing provides new possibilities for remote detection [Laser Phys. Lett., 8(10), 736-741 (2011)]. [Preview Abstract] |
Monday, March 2, 2015 9:12AM - 9:48AM |
A3.00003: Dynamics of Molecular Gyroscopes Created by Strong Optical Fields Invited Speaker: Amy Mullin We explore the behavior of molecules in ultra-high angular momentum states prepared in an optical centrifuge and detected with transient IR absorption spectroscopy. In the optical centrifuge, the polarizable electron cloud of molecules interacts with the electric field of linearly polarized light that angularly accelerates over the time of the optical pulse. The centrifuge pulse is generated by combining oppositely chirped pulsed of light. Trapped molecules are driven into high angular momentum states that are spatially oriented with the optical field and have energies far above the average at 300 K. High resolution transient IR spectroscopy reveals the dynamics of collisional energy transfer for the super-rotors. Polarization-dependent studies show that the initial angular momentum orientation persists for many collisions, indicating that molecules in an optical centrifuge behave as quantum gyroscopes. Time-dependent population and energy profiles for individual J- states give information about the dynamics of super-rotors. [Preview Abstract] |
Monday, March 2, 2015 9:48AM - 10:24AM |
A3.00004: An Alternative to Laser Cooling Invited Speaker: Mark Raizen Laser cooling has been the standard approach for over thirty years for cooling the translational motion of atoms. While laser cooling is an extremely successful method, it has been limited to a small set of elements in the periodic table. The performance of laser cooling for those elements has saturated in terms of flux of ultra-cold atoms, density, and phase-space density. I report our progress towards the development of an alternative to laser cooling. Our approach relies on magnetic stopping of supersonic beams, an atomic coilgun. A recent advance is the experimental realization of an adiabatic coilgun which preserves phase-space density. Further cooling was demonstrated with a one-way wall, realizing the historic thought experiment of Maxwell's Demon. More recently, we showed how to apply this method to compress atomic phase space with almost no loss of atom number. Our approach is fundamentally different than laser cooling as it does not rely on the momentum of the photon, but rather the photon entropy. I will report on our experimental progress towards this goal, and describe future experiments that will be enabled by this work. [Preview Abstract] |
Monday, March 2, 2015 10:24AM - 11:00AM |
A3.00005: MHz Resolution Imaging Spectroscopy Invited Speaker: David Chandler Velocity Mapped Ion Imaging has been used for the measurement of the velocity of molecules with resolution down to 1 meter per second. Because of this high velocity resolution one can use this technique to measure spectroscopic features with 1 MHz resolution. We demonstrate this ability on Kr atoms. A thermal distribution of Kr atoms is present in our Ion Imaging apparatus, we will use a three-photon scheme to ionize the Kr atoms, with one of the photon steps being supplied by a high resolution CW laser. By observing the portion of the Doppler width that is ionized by this combination of lasers one can determine the absolute frequency of the laser relative to the line center of the Kr transition, the power broadening associated with the cycling of the Kr atoms with the CW laser, the power broadening associate with the ionization laser and observe Zeeman splittings in the Doppler width of the Kr atom transition. The ability to visualize the photo-physics of the ionization process gives demonstrates how we can use this technique as a molecular wave meter. [Preview Abstract] |
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