TY - JOUR
T1 - Internal conversion mediated by specific nuclear motions
T2 - the nitrogen inversion in amines
AU - Klein, Liv Bærenholdt
AU - Sølling, Theis Ivan
N1 - Papers from the 11th International Conference on Femtochemistry (FEMTO11) that took place at The Technical University of Denmark (DTU), Copenhagen
PY - 2014/10/17
Y1 - 2014/10/17
N2 - To investigate the influence of amine structure on the internal conversion from S2 to S1, three aliphatic amines containing the same number of degrees of freedom, but with different degree of N-substitution, were investigated with femtosecond time-resolved mass spectrometry. As N-substituents lower the excitation energies, and the excitation in all cases is by a 200 nm photon, the S1 density-of-states in the Franck-Condon region will be high for the more N-alkylated amine. This, according to standard models, should lead to faster internal conversion. The experimental results are in contrast to this, indicating non-ergodic behavior and a coupling of the states by very few molecular vibrations. This was further investigated by substituting differing numbers of hydrogen atoms with deuterium in two amines, one primary and one tertiary, thus freezing the degrees of freedom while altering the N-substituent mass. In both case, deuteration resulted in a significantly longer lifetime of the initially excited state, confirming the importance of the N-inversion motion in the description of the dynamics of internal conversion.
AB - To investigate the influence of amine structure on the internal conversion from S2 to S1, three aliphatic amines containing the same number of degrees of freedom, but with different degree of N-substitution, were investigated with femtosecond time-resolved mass spectrometry. As N-substituents lower the excitation energies, and the excitation in all cases is by a 200 nm photon, the S1 density-of-states in the Franck-Condon region will be high for the more N-alkylated amine. This, according to standard models, should lead to faster internal conversion. The experimental results are in contrast to this, indicating non-ergodic behavior and a coupling of the states by very few molecular vibrations. This was further investigated by substituting differing numbers of hydrogen atoms with deuterium in two amines, one primary and one tertiary, thus freezing the degrees of freedom while altering the N-substituent mass. In both case, deuteration resulted in a significantly longer lifetime of the initially excited state, confirming the importance of the N-inversion motion in the description of the dynamics of internal conversion.
KW - Amines
KW - Internal conversion
KW - Non-ergodicity
KW - Time-resolved mass spectrometry
U2 - 10.1016/j.chemphys.2014.02.017
DO - 10.1016/j.chemphys.2014.02.017
M3 - Journal article
AN - SCOPUS:84907902651
SN - 0301-0104
VL - 442
SP - 62
EP - 67
JO - Chemical Physics
JF - Chemical Physics
ER -