Controlling the quantum numbers in chemical reactions

Electron transfer mediates vibrational relaxation of CO in collisions with Ag(111)

We report vibrational relaxation probabilities for CO(v = 17) scattered from Ag(111) and compare our results to studies on other molecule–surface systems, which indicates a clear dependence of the relaxation probability on the work function of the surface and the electron binding energy of the molecule.

Electronically non-adiabatic influences in surface chemistry and dynamics

Electronically nonadiabatic interactions between molecules and metal surfaces are now well known. But evidence that such interactions influence reaction rates is still scarce. This paper reviews research related to this topic and proposes pathways forward.

The role of angular momentum in collision-induced vibration–rotation relaxation in polyatomics

Vibrational relaxation of the 6(1) level of S(1)((1)B(2u)) benzene is analyzed using the angular momentum model of inelastic processes. Momentum-(rotational) angular momentum diagrams illustrate energetic and angular momentum constraints on the disposal of released energy and the effect of collision partner on resultant benzene rotational excitation. A kinematic "equivalent rotor" model is introduced that allows quantitative prediction of rotational distributions from inelastic collisions in polyatomic molecules. The method was tested by predicting K-state distributions in glyoxal-Ne as well as J-state distributions in rotationally inelastic acetylene-He collisions before being used to predict J and K distributions from vibrational relaxation of 6(1) benzene by H(2), D(2), and CH(4). Diagrammatic methods and calculations illustrate changes resulting from simultaneous collision partner excitation, a particularly effective mechanism in p-H(2) where some 70% of the available 6(1)-->0(0) energy may be disposed into 0-->2 rotation. These results support the explanation for branching ratios in 6(1)-->0(0) relaxation given by Waclawik and Lawrance and the absence of this pathway for monatomic partners. Collision-induced vibrational relaxation in molecules represents competition between the magnitude of the energy gap of a potential transition and the ability of the colliding species to generate the angular momentum (rotational and orbital) needed for the transition to proceed. Transition probability falls rapidly as DeltaJ increases and for a given molecule-collision partner pair will provide a limit to the gap that may be bridged. Energy constraints increase as collision partner mass increases, an effect that is amplified when J(i)>0. Large energy gaps are most effectively bridged using light collision partners. For efficient vibrational relaxation in polyatomics an additional requirement is that the molecular motion of the mode must be capable of generating molecular rotation on contact with the collision partner in order to meet the angular momentum requirements. We postulate that this may account for some of the striking propensities that characterize polyatomic energy transfer.

The dynamics of "stretched molecules": experimental studies of highly vibrationally excited molecules with stimulated emission pumping

We review stimulated emission pumping as used to study molecular dynamics. The review presents unimolecular as well as scattering studies. Topics include intramolecular vibrational redistribution, unimolecular isomerization and dissociation, van der Waals clusters, rotational energy transfer, vibrational energy transfer, gas-surface interactions, atmospheric effects resulting from nonequilibrium vibrational excitation, and vibrational promotion of electron transfer.

Temperature Dependence of Collisional Deactivation of Highly Vibrationally Excited Biphenylene

Collisional energy transfer between highly vibrationally excited biphenylene and a variety of mono- and polyatomic bath gases has been measured at temperatures between 333 and 523 K. Biphenylene molecules were initially prepared with an additional vibrational energy of 28490 cm