The decay of infrared fluorescence from IR multiphoton excited CDCl 3 was studied as a function of incident fluence and pressure of added Ar. The decays were exponential and allowed for the calculation of the average energy transferred per collision, 〈〈∆E〉〉, with Ar and with CDCl 3 , as a function of the average internal energy of excited CDCl 3 using a direct method. Identical information was obtained following the inversion procedure developed by Barker et al. (Int. ReV. Phys. Chem. 1993, 12, 2, 305). Both sets of values agree well for a single value of the internal energy. The experimental results were also modeled using a master equation formulation to obtain 〈∆E〉 d , confirming the predictive power of the model calculations. The increase of temperature of the gas mixture and its effect on the IR fluorescence signal were also analyzed.

The time variation of the 2v fluorescence intensity was measured in CDC13 excited in the V C-D bending mode by a TEA CO laser operating on the 10P(48) line. A fast rise of the fluorescence, with a time constant < 1/.is Torr, was first observed, showing that a fast equilibration of population occurs between the v and v5 modes through a v <-+ v5 Coriolis-assisted intermode transfer and a v5 <-+ 2v5 near-resonant ladder-climbing process. Then a first fast fluorescence decay was observed and attributed to a (v 4, vs)-+ v2 intermode transfer with a rate constant of (7.10 + 1.13)ms-t Torr-t. At last, a much slower decay, with a rate constant of 0.111 + 0.015 ms-Torr-, results from the less efficient intermode transfer and V-T,R deexcitation processes involving the v and v states, and which compete to relax the gas to a thermodynamic equilibrium.

We discuss the topological analysis of dynamical systems represented by two-dimensional maps emphasizing the case of Poincaré maps. The central result consists in the implementation of a recent presentation of braids as deformations of circles ͓M. A. Natiello and H. G. Solari, J. Knot Theory Ramifications 3, 511 ͑1994͔͒ to the determination of braid types associated with periodic orbits ͑up to a global torsion͒. Since some braids imply positive topological entropy, the topological analysis can be regarded as a test of chaos. The method is specially suited for experiments where the complete reconstruction of the phase space for the flow cannot be achieved at a reasonable cost. We apply these ideas to data sets produced in a laser physics experiment for which the reconstruction of the phase space of the flow is nearly impossible. ͓S1063-651X͑96͒03309-0͔PACS number͑s͒: 05.45.bϩ, 42.65.Sf, 47.20.Ky