Photodissociation of [Ar–N2]+ induced by near-IR femtosecond laser fields by ion-trap time-of-flight mass spectrometry.

Photodissociation of [Ar–N2]+ induced by a near-IR (800 nm) femtosecond laser pulse is investigated using ion-trap time-of-flight mass spectrometry. The intra-complex charge transfer proceeding in the course of the decomposition of the electronically excited Ar+(2P3/2)⋯N2(X1Σg+), prepared by the photoexcitation of the electronic ground Ar(1S0)⋯N2+(X2Σg+), is probed by the ion yields of Ar+ and N2+. The yield ratio γ of N2+ with respect to the sum of the yields of Ar+ and N2+ is determined to be γ = 0.62, which is much larger than γ ∼ 0.2 determined before when the photodissociation is induced by a nano-second laser pulse in the shorter wavelength region between 270 and 650 nm. This enhancement of γ at 800 nm and the dependence of γ on the excitation wavelength are interpreted by numerical simulations, in which the adiabatic population transfer from Ar+(2P3/2)⋯N2(X1Σg+) to Ar(1S0)⋯N2+(X2Σg+) at the avoided crossings is accompanied by the vibrational excitation in the N2+(X2Σg+) moiety followed by the intra-complex vibrational energy transfer from the N2+(X2Σg+) moiety to the intra-complex vibrational mode leading to the dissociation. [ABSTRACT FROM AUTHOR]