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Dynamics and the breaking of a driven cage: I2 in solid Ar.
Z Bihary1, R Zadoyan, M Karavitis
1Department of Chemistry, University of California, Irvine, California 92697, USA.
The Journal of Chemical Physics
|July 23, 2004
Summary
Impulsive excitation of iodine (I2) in solid noble gases reveals detailed cage dynamics. The cage rebounds, resonates, and can break, leading to molecular dissociation and lattice disruption.
Area of Science:
- Physical Chemistry
- Condensed Matter Physics
- Spectroscopy
Background:
- Understanding molecular behavior within solid matrices is crucial for various applications.
- Previous studies have explored guest-host interactions, but detailed dynamics of cage response to impulsive excitation remain less understood.
Purpose of the Study:
- To characterize the cage response of solid noble gases (Ar, Kr, Xe) to impulsive excitation of embedded iodine molecules (I2).
- To investigate the dynamics from initial excitation to cage breaking and molecular dissociation.
Main Methods:
- Utilized pump-probe spectroscopy to measure the dynamics of I2 in solid Ar, Kr, and Xe.
- Analyzed wavepacket motion on dissociative potentials to probe local dynamics and cage response.
- Investigated polarization-selective multiphoton dissociation kinetics.
Main Results:
- Observed cage rebounds with a characteristic period of 1.2 ps, largely independent of excitation amplitude.
- Identified cage ringing as a local resonant mode in Ar (1 ps period) and at the Debye edge in Kr and Xe.
- Determined that a 4 eV excess energy kick breaks the Ar cage with 50% probability, leading to dissociation and lattice disruption.
Conclusions:
- The chromophore (I2) acts as a transducer, driving and reporting on cage dynamics.
- Cage breaking involves lattice destruction, creating interstitials and vacancies.
- Observed nonadiabatic spin-flip transitions during large amplitude cage motion, occurring with unit probability in Ar beyond 6 Å bond stretch.