Controlling high harmonic generation with molecular wave packets

We show that, by controlling the alignment of molecules, we can influence the high harmonic generation process. We observed strong intensity modulation and spectral shaping of high harmonics produced with a rotational wave packet in a low-density gas of N\u2082 or O\u2082. In N\u2082, where the highest occupied molecular orbital (HOMO) has \u3c3g symmetry, the maximum signal occurs when the molecules are aligned along the laser polarization while the minimum occurs when it is perpendicular. In O\u2082, where the HOMO has \u3c0g symmetry, the harmonics are enhanced when the molecules are aligned around 45\ub0 to the laser polarization. The symmetry of the molecular orbital can be read by harmonics. Molecular wave packets offer a means of shaping attosecond pulses.Peer reviewed: YesNRC publication: Ye