Quantum control of light-induced reactions

K. Hakuta, M. Katsuragawa

Xuan Li, Gregory A. Parker, Paul W. Brumer +2 more

We present a nonperturbative time-dependent quantum mechanical theory of the laser catalysis and control of a bifurcating A+BC<-->(variant Planck's over 2pi omega(0))ABC*(v)<-->(variant Planck's over 2pi omega(0) )AB+C reaction, with ABC*(v) denoting an intermediate, electronically excited, complex of ABC in the vth vibrational state. We apply this theory to the low collision energy fermion-boson light-induced exchange reaction, (6)Li((2)S)+(7)Li(2)((3)Sigma(u)(+))<-->(variant Planck's over 2pi omega(0))((6)Li(7)Li(7)Li)*<-->(variant Planck's over 2pi omega(0))(6)Li(7)Li((3)Sigma(+))+(7)Li((2)S). We show that at very low collision energies and energetically narrow (approximately 0.01 cm(-1)) initial reactant wave packets, it is possible to tune the yield of the exchange reaction from 0 to near-unity (yield >or=99%) values. Controllability is somewhat reduced at collisions involving energetically wider (approximately 1 cm(-1)) initial reactant wave packets. At these energetic bandwidths, the radiative reactive control, although still impressive, is limited to the 0%-76% reactive-probabilities range.

Alan Lenef, D. Kreysar, K. Obermyer +1 more

Radiation tuned to an excited-state transition in dense cesium vapor results in the appearance of induced absorption and fluorescence after delays of up to 5 s, an observation ascribed to a chain reaction of resonant binary collisions initiated by the incident light. Our results occur in a nonlinear regime characterized by high collision rates, which are variable in a controlled fashion at constant vapor density.

Hermann Uys, Ismail Yunus Akhalwaya, N Botha +8 more

Hui Li, Ming Li, Alexander Petrov +2 more

High Resolution Image Download MS PowerPoint Slide Conical intersections are crossing points or lines between two or more adiabatic electronic potential energy surfaces in the multidimensional coordinate space of colliding atoms and molecules. Conical intersections and corresponding nonadiabatic coupling can greatly affect molecular dynamics and chemical properties. In this paper, we predict significant or measurable nonadiabatic effects in an ultracold atom–ion charge-exchange reaction in the presence of laser-induced conical intersections (LICIs). We investigate the fundamental physics of these LICIs on molecular reactivity under unique conditions: those of relatively low laser intensity of 10 8 W/cm 2 and ultracold temperatures below 1 mK. We predict irregular interference effects in the charge-exchange rate coefficients between K and Ca + as functions of the laser frequency. These irregularities occur in our system due to the presence of two LICIs. To further elucidate the role of the LICIs on the reaction dynamics, we compare these rate coefficients with those computed for a system where the CIs have been “removed”. In the laser frequency window, where conical interactions are present, the difference in rate coefficients can be as large as 1 × 10 –9 cm 3 /s.

Hans‐A. Bachor