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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) July 31, 2015

Constraining the Conformational Landscape of a Polyether Building Block by Raman Jet Spectroscopy

Sebastian Bocklitz and Martin A. Suhm

Abstract

Collisionally induced chain isomerization of CH3OCH2CH2OCH3 around its three central torsional angles is characterized in a supersonic slit jet by probing compound-seeded carrier gas expansions with focussed 5–25 W cw 532 nm radiation as a function of carrier gas, nozzle temperature and distance. Spontaneously Raman scattered photons are collected and dispersed down to 100 cm1. They reveal important contributions from three chain conformations in the expansion. Isomerization around the outer torsional angle is found to be feasible, whereas the central OCCO angle remains largely conserved under most expansion conditions. The spectroscopic results are used for a critical assessment of quantum-chemical predictions for the energy sequence of the three low-lying conformations. The stretched global minimum energy structure of this polyether building block is consistent with a statistical model of the dominant unimolecular relaxation pathways.

Acknowledgement

The authors would like to thank K. Otto for help and discussions. We are grateful to Spectra-Physics and Coherent for making 25 W Millenia and 18 W Verdi G lasers available for part of these experiments and to the DFG for generous support (project SU 121/2).

Received: 2015-4-21
Accepted: 2015-7-13
Published Online: 2015-7-31
Published in Print: 2015-10-28

©2015 Walter de Gruyter Berlin/Boston