- Yong, Haiwang;
- Xu, Xuan;
- Ruddock, Jennifer M;
- Stankus, Brian;
- Carrascosa, Andrés Moreno;
- Zotev, Nikola;
- Bellshaw, Darren;
- Du, Wenpeng;
- Goff, Nathan;
- Chang, Yu;
- Boutet, Sébastien;
- Carbajo, Sergio;
- Koglin, Jason E;
- Liang, Mengning;
- Robinson, Joseph S;
- Kirrander, Adam;
- Minitti, Michael P;
- Weber, Peter M
Intramolecular charge transfer and the associated changes in molecular structure in N,N'-dimethylpiperazine are tracked using femtosecond gas-phase X-ray scattering. The molecules are optically excited to the 3p state at 200 nm. Following rapid relaxation to the 3s state, distinct charge-localized and charge-delocalized species related by charge transfer are observed. The experiment determines the molecular structure of the two species, with the redistribution of electron density accounted for by a scattering correction factor. The initially dominant charge-localized state has a weakened carbon-carbon bond and reorients one methyl group compared with the ground state. Subsequent charge transfer to the charge-delocalized state elongates the carbon-carbon bond further, creating an extended 1.634 Å bond, and also reorients the second methyl group. At the same time, the bond lengths between the nitrogen and the ring-carbon atoms contract from an average of 1.505 to 1.465 Å. The experiment determines the overall charge transfer time constant for approaching the equilibrium between charge-localized and charge-delocalized species to 3.0 ps.