Multiphoton dissociation of molecules with low power cw infrared lasers: collisional enhancement of dissociation probabilities

Abstract

Multiphoton dissociation of C3F+6 is observed using low intensity cw CO2 laser radiation. Ion cyclotron resonance (ICR) techniques are used to store ions for irradiation. Ion storage times up to 2 s are used. Multiphoton dissociation is observed at laser intensities below 100 W cm−2 and at pressures below 10−5 Torr. Only the lowest energy decomposition of C3F+6, to give C2+4 and CF2, is observed. Multiphoton dissociation probabilities show a sharp wavelength dependence in contrast to typical pulsed laser multiphoton dissociation experiments. The photodissociation spectrum of C3F+6 is similar to the infrared absorption spectrum of neutral C3F6 at both low and high resolution. Collisions between C3F+6 and unreactive buffer gases (Ar, N2, SF6) are seen to enhance multiphoton dissociation, while collisions with C3F6 deactive the laser excited species. The results are discussed in terms of mechanisms for slow multiphoton dissociation.