Computer simulation of mechanisms of the SIMOX process

Reiss, S.

doi:10.1016/0168-583x(95)00280-4

Cited by 15 publications

(1 citation statement)

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“…27,28 The intensity jump in the preannealed sample, which must be associated with the motion of micrometer-size grains, takes place on the time scale of 1 min ͑the scan time of the entire trace is 4 min͒. The effect is suggestive of sintering or Ostwald ripening, 29,30 which can occur if defects have significant mobility. At 128 K, while defects in ice are locked, a glass transition is known to connect the low-density amorphous phase to the frozen "water B" phase.…”

Section: X-state Dynamicsmentioning

confidence: 99%

Vibronic dynamics of I2 trapped in amorphous ice: Coherent following of cage relaxation

Senekerimyan

Goldschleger

Apkarian

2007

The Journal of Chemical Physics

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Four-wave mixing measurements are carried out on I(2)-doped ice, prepared by quench condensing the premixed vapor at 128 K. Coherent vibrational dynamics is observed in two distinct ensembles. The first is ascribed to trapping in asymmetric polar cages in which, as in water, the valence absorption of the molecule is blueshifted by 3500 cm(-1), predissociation of the B state is complete upon the first extension of the molecular bond, and the vibrational frequency in the ground state (observed through coherent anti-Stokes Raman scattering) is reduced by 6.5%. The effect is ascribed to polarization of the molecule. The implied local field and the ionicity of the molecule are extracted, to conclude that the molecule is oxygen bonded to one water molecule on one side and hydrogen bonded on the other side. The second ensemble is characterized by the transient grating signal, which shows coherent vibrational dynamics on the B state. The small predissociation rate in this site suggests a symmetric cage in which the local electric field undergoes effective cancellation; and consistent with this, the extracted blueshift of the valence transition in this site (approximately 1500 cm(-1)) coincides with that observed in clathrate hydrates of iodine. Remarkably, in this site, the vibrational period of the B state packet coherently stretches from an initial value of 245 fs to 325 fs in the course of five oscillations (1.3 ps), indicative of vibrationally adiabatic following of the cage expansion. The dynamics is characteristic of a molecule trapped in a tight symmetric cage, with a soft cage coordinate that relaxes without eliciting elastic response. Enclathration in low-density amorphous ice is concluded.

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Section: X-state Dynamicsmentioning

confidence: 99%