Dynamics and the breaking of a driven cage: I2 in solid Ar

Abstract

Pump-probe measurements of I2 in solid Ar are reported and analyzed to extract a description of cage response to impulsive excitation, from the gentle kick, up to the breaking point. The most informative data are obtained through wavepacket motion on cage-bound, but otherwise dissociative, potentials where the chromophore acts as a transducer to drive the cage and to report on the local dynamics. This general class of dynamics is identified and analyzed as a function of energy in Ar, Kr, and Xe. The overdriven cage rebounds with a characteristic period of 1.2 ps that shows little dependence on excitation amplitude in all hosts. After rebound, the cage rings as a local resonant mode in Ar, with a period of 1 ps and dephasing time of 3 ps. This mode remains at the Debye edge in Kr and Xe, with periods of 630 and 800 fs, and dephasing times of 8 and 6 ps, respectively. In the bound B-state, the cage fluctuates toward its dilated equilibrium structure on a time scale of 3 ps, which is extracted from the down-chirp in the molecular vibrational frequency. When kicked with excess energy of 4 eV, the Ar cage breaks with 50% probability, and the molecule dissociates. The kinetics of polarization selective, multiphoton dissociation with Gaussian laser intensity profiles is delineated and the ballistics of cage breakout is described: The photodissociation proceeds by destruction of the local lattice, by creating interstitials and vacancies. During large amplitude motion on cage-bound potentials, sudden, nonadiabatic spin-flip transitions can be observed and quantified in space and time. The spin-flip occurs with unit probability in Ar when the I*-I bond is stretched beyond 6 A.

Dissipative quantum coherent dynamics probed in phase-space: Electronically resonant 5-color 4-wave mixing on I2(B) in solid Kr

“…7 agree with prior pu-pr determinations. 34 The notable difference in the present is the interweaving of the AS-and S-periods, which clock ϕ 1 and ϕ 2 , respectively. In one cycle, ϕ 1 loses ∼300 cm −1 …”

Electronic spectroscopy of I2–Xe complexes in solid Krypton

“…Exciting the I 2 /Kr matrix with ArF laser results also in a weak emission in the UVregion at 31 200 cm −1 , now assigned as F → a transition. 25 Most pronounced change in emission as function of Xe doping (between 0.1% and 2%) is a systematic loss of intensity from the main emission structure and the visible region emissions relative to the UV-emission. The intensity loss effect is very dramatic even with our lowest Xe ratio of 0.1%, and continues systematically to higher Xe ratios.…”

“…Alternative explanation for the observed VUV transitions has also been suggested by Bihary et al, based on different bleaching rates of the absorptions upon 193 nm excitation and the gas-phase energetics of the IP states. 25 They tentatively argued that the red-wing (now assigned as impurity) is actually the parallel X → D and the main emission is the perpendicular X → γ (1 u ) separated in the gas-phase by ∼600 cm −1 . The generated dichroism when unpolarized light is used is responsible for the lack of intensity in X → D. Even though we cannot completely refute this argument, because of we have not measured our VUV spectra with polarized optics, their argument seems very unlikely in the light our observation of the increasing intensity in the redshifted band as a function of storage time.…”

“…Time-domain pump-probe dynamics of the I 2 A( 3 1u )-state has been analyzed with great detail in the rare gas matrices, 4,[45][46][47] mainly from the point of view of cage recombination and predissociation to the A state. The negative time signal in the panel (c) reflects slow Kr cage dynamics 25,48 (period ∼630 fs) seen through the first IP tier emissions. We propose a multiphoton (1 × 620 nm + 2 × 558 nm) excitation route through the cage bound Astate (see Figure 1 panel (c)) as the main source for our signal in the negative time delays.…”

“…This was also the proposed mechanism in a similar experiment by Bihary et al in solid argon. 25 We investigated the Xe doped matrix also with pulse energies: λ Pump = 558 nm and λ Probe = 500 nm. Using these energies strong first IP tier emissions can be observed with a definite B-state oscillation period up to 5 ps (see supplementary material S3 for details 29 ).…”