TY - JOUR
T1 - Symmetry species conversion in rotational tunneling systems observed by hole burning
T2 - high resolution spectroscopy of dimethyl-s-tetrazine in n-octane
AU - Orth, K.
AU - Schellenberg, P.
AU - Friedrich, J.
AU - Häusler, W.
N1 - Funding Information:
We thank the DFG (Graduiertenkolleg “Nicht-lineare Dynamik” and SFB2I3-B15) and the Fonds der Chemischen Industrie. W.H. acknowledges support from DFG project No. AP 47/1-1. We appreciate the discussions on this subject with P. Trommsdorff, B. Prass and M. Joyeux during the hole burning meeting in Ascona. We acknowledge numerous very fruitful conversations with Gregor Diezemann about conversion rates in deuterated systems. We thank Dr. Reiner for taking the NMR spectra of isotopically labelled dimethyl-s-tetrazine.
PY - 1993/10
Y1 - 1993/10
N2 - We present a summary of our results on methyl group spectroscopy and relaxation measurements of the dye molecule dimethyl-s-tetrazine and its CD3- and CDH2-substituted derivatives in a n-octane host. In the CH3- and CD3-substituted derivatives, two hole burning mechanisms occur: one is based on nuclear spin-transformation, the other is a structural transformation. The mechanism based on spin transformation leads to sharp antiholes, spaced by 37 and 20 GHz from the burning laser frequency for CH3 and CD3, respectively. The structural burning mechanism leads to side holes. Surprisingly, the splitting of the side holes is different from that of the antiholes. This phenomenon is interpreted in terms of two different dye species, which are distinguished through their local environment. Both species have very different yields for the structural and the nuclear spin phototransformation process. From the recovery of the central hole, the relaxation of the rotational tunneling states was measured as a function of temperature. The data support a Raman-type phonon scattering process. Deuteration does not slow down the relaxation but, instead, increases it by almost two orders of magnitude. According to our knowledge these are the first measurements of symmetry species conversion times of isotopic derivatives of methyl groups. Within the assumption of a Raman-type conversion mechanism we estimate a rather low hindering potential barrier for the rotors.
AB - We present a summary of our results on methyl group spectroscopy and relaxation measurements of the dye molecule dimethyl-s-tetrazine and its CD3- and CDH2-substituted derivatives in a n-octane host. In the CH3- and CD3-substituted derivatives, two hole burning mechanisms occur: one is based on nuclear spin-transformation, the other is a structural transformation. The mechanism based on spin transformation leads to sharp antiholes, spaced by 37 and 20 GHz from the burning laser frequency for CH3 and CD3, respectively. The structural burning mechanism leads to side holes. Surprisingly, the splitting of the side holes is different from that of the antiholes. This phenomenon is interpreted in terms of two different dye species, which are distinguished through their local environment. Both species have very different yields for the structural and the nuclear spin phototransformation process. From the recovery of the central hole, the relaxation of the rotational tunneling states was measured as a function of temperature. The data support a Raman-type phonon scattering process. Deuteration does not slow down the relaxation but, instead, increases it by almost two orders of magnitude. According to our knowledge these are the first measurements of symmetry species conversion times of isotopic derivatives of methyl groups. Within the assumption of a Raman-type conversion mechanism we estimate a rather low hindering potential barrier for the rotors.
UR - https://www.scopus.com/pages/publications/0027681804
U2 - 10.1016/0022-2313(93)90060-Z
DO - 10.1016/0022-2313(93)90060-Z
M3 - Article
AN - SCOPUS:0027681804
SN - 0022-2313
VL - 56
SP - 99
EP - 108
JO - Journal of Luminescence
JF - Journal of Luminescence
IS - 1-6
ER -