Probing intermolecular communication via lattice phonons with time-resolved coherent anti-Stokes Raman scattering†

† Special number of Molecular Physics in honor of Robert A. Harris.

Abstract

Calculations are presented demonstrating controlled intermolecular communication between dopant molecules via lattice phonons in a cryogenic matrix. By simulating a time-resolved coherent anti-Stokes Raman scattering (tr-CARS) experiment on an I₂-molecule ‘receiver,’ its reception from a Ca-atom ‘transmitter’ of coherent lattice waves in a compressed linear chain of Ar atoms is monitored. A short pulse resonant with an atomic transition in Ca arrives at the sample before the tr-CARS pulses, and the coherent response of the host medium to the electronic excitation sends a rarefaction wave through the lattice. The arrival of this propagating distortion at the I₂ molecule is detected through the tr-CARS difference signal, the difference between tr-CARS signals with and without the Ca pulse. A normal-mode analysis of the equilibrium configuration is used to construct an initial Gaussian wave packet, which is propagated by locally quadratic approximations to the relevant many-body nuclear Hamiltonians. Results are presented for both resonant and sub-resonant excitation of the Ca atom. Calculations show a difference signal that turns on abruptly as the lattice wave generated by resonant Ca excitation reaches the I₂ chromophore.

† Special number of Molecular Physics in honor of Robert A. Harris.

Acknowledgements

With admiration and appreciation, we dedicate this paper to the second author's former thesis advisor and life-long friend, Bob Harris. The research was supported by grants from the US National Science Foundation and the ACS-PRF, and a Fellowship to JAC from the J. S. Guggenheim Memorial Foundation. We gratefully acknowledge helpful advice from Professor David Herrick, University of Oregon, on the compact parametrization of the I₂ RKR potentials, and many beneficial conversations with Ara Apkarian, UC-Irvine. We thank Professor Edward Caster, Rutgers University, who pointed out the connection between our work and the measurements of 25–28.

Notes

‡Current address: Walsh University, North Canton, OH 44720 USA.

† Special number of Molecular Physics in honor of Robert A. Harris.

Additional information

Notes on contributors

M. A. Rohrdanz‡

‡Current address: Walsh University, North Canton, OH 44720 USA.