1. Department
of Physics, Wesleyan University, Middletown, Connecticut 06457, United States
2. Laboratoire
de Spectroscopie Ultrarapide (LSU) and Lausanne Centre for Ultrafast
Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC, FSB, CH-1015 Lausanne, Switzerland
3. Molecular
Biophysics Program, Wesleyan University, Middletown, Connecticut 06457, United States