Impulsive Collision Dynamics of CO Super Rotors from an Optical Centrifuge. Issue 22 (20th October 2016)

• Record Type: Journal Article
• Authors: Murray, Matthew J.; Ogden, Hannah M.; Toro, Carlos; Liu, Qingnan; Mullin, Amy S.
• Is Part Of: Chemphyschem. Volume 17:Issue 22(2016)
• Page Start: 3692
• Page End: 3700
• Publication Date: 2016-10-20
• Subjects: collision dynamics -- energy transfer -- molecular dynamics -- super rotors -- time-resolved spectroscopy; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201600871
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: We report state‐resolved collision dynamics for CO molecules prepared in an optical centrifuge and measured with high‐resolution transient IR absorption spectroscopy. Time‐resolved polarization‐sensitive measurements of excited CO molecules in the J =29 rotational state reveal that the oriented angular momentum of CO rotors is relaxed by impulsive collisions. The translational energy gains for molecules in the initial plane of rotation are threefold larger than for randomized angular momentum orientations, indicating the presence of anisotropic kinetic energy. The transient data show enhanced population for CO molecules in the initial plane of rotation immediately following the optical centrifuge pulse. A comparison with previous CO2 super rotor studies illustrates the behavior of molecular gyroscopes; spatial reorientation of CO2 J =76 rotors takes substantially longer than that for CO J =29 rotors, despite similarities in classical rotational period and rotational energy gap. High‐resolution transient IR absorption measurements of the CO J =29–39 rotational states show that the collisional depopulation rates increase with J quantum number. Abstract : Molecular gyroscopes : An ensemble of highly rotationally excited CO molecules with oriented angular momentum (see picture) is prepared in an optical centrifuge. The CO rotors undergo collision‐induced rotational relaxation with a behavior characterized by large velocities parallel to the initial plane of rotation and retention of their initial spatial orientation.