Dynamic Stark shift of the³R₁Rydberg state of CH₃I

Abstract

Abstract. Stark shift of the 3 R 1 Rydberg state of CH 3 I is measured for different Stark field intensities. Photodissociation products, generated after predissociation of the state, were detected when the molecules were excited with photons resonant with the energy difference between the ground and the shifted 3 R 1 state, allowing the shift to be quantified. Qualitative agreement has been found with a 1D model.

Strong laser field control of fragment spatial distributions from a photodissociation reaction

“…Dynamic Stark control (DSC) 14 was shown to cause resonance shifts in the B -band of CH 3 I 10 , and the combination of this effect with pump-dump strategies 40, 41 was capable of causing dramatic changes in the predissociation lifetime and the product branching ratio. Indeed, the introduction of an intense infrared field opened new dynamical channels for the initially populated Rydberg state of the molecule, the most interesting of which was a pump-dump channel coupling the initially populated 3 R 1 Rydberg state with the 3 Q 1 dissociative surface (see Fig.…”

“…3c is the corresponding asymptotic Abel-inverted methyl fragment image. The excitation laser wavelength had to be retuned in this case to 200.6 nm (see Experimental section) to recover the resonance due to the Stark shift induced by the high intensity field 9, 10 . The same two channels described for the previous case in the above paragraph (predissociation CH 3 ( ν  = 0) + I*( 2 P 1/2 ), and pump-dump CH 3 ( ν  = 0) + I( 2 P 3/2 )) are present now, but their angular character is notably different, the predissociation channel presenting a much more pronounced perpendicular character at asymptotic times and the pump-dump channel showing a lobular character with maxima at ±45° with respect to the laser polarization direction.…”

“…The essential tool in these schemes is a control laser pulse that is precisely defined in terms of spectrum, time, intensity and polarization. A significant number of theoretical proposals and experimental demonstrations of laser control have been presented 3–6 showing laser-induced modifications of observables like the absorption spectrum 7–10 , lifetimes 9, 11–13 , quantum yields 14–16 or even spatial localization of molecules in space 17 .…”

Femtosecond Photodissociation Dynamics by Velocity Map Imaging. The Methyl Iodide Case

“…Relatively minor experimental changes are required to explore other interesting phenomena with a very similar experimental scheme, like, for instance, Coulomb explosion [60,61]. Also, the possibilities for strong-field control through the introduction of an additional IR ultrashort laser field have been explored with success [62,63]. More and more systems are becoming amenable to be studied by femtosecond velocity map imaging, and there are now examples for small molecules like ammonia [64,65] or larger molecules like organic chromophores [66][67][68][69][70][71][72].…”

Molecular events in the light of strong fields: A light‐induced potential scenario

“…The first obvious effect is the Stark shift of the photodissociation bands, thus changing the spectrum. [117] If several dissociation channels are present, one can use a pump pulse in combination with a strong nonresonant pulse to separate the different channels. [106] However, the field also couples the different excited states so that the dissociation occurs on a "mixed" channel, that is, on a superposition of excited electronic states correlating to different channels.…”