Molecular dissociation of HD$^+$ by broad bandwidth chirped laser pulses: a molecular bandwidth filter

We employ a coincidence 3D momentum imaging method to study the fragmentation of HD$^+$ following interaction with an intense, 800 nm, 25 fs Fourier transform-limited (FTL) laser pulse. The broad bandwidth of our FTL pulse prevents us from observing vibrational peaks that one would expect to see using longer FTL laser pulses $\sim$100 fs. However, by chirping the pulse either positively or negatively, while maintaining a fixed bandwidth, we were able to measure vibrational structure. The kinetic energy release of these vibrational peaks are shifted up or down depending on the sign of the chirp.\footnote{V.~S.~Prabhudesai \textit{et al.}, \textit{Phys. Rev. A} \textbf{81}, 023401 (2010).} We will address the question of why the vibrational structure is observed in spite of the broad bandwidth of the chirped laser pulses.