Two-photon absorption of dissociating TLI in strong laser fields

Abstract

In a strong laser field (I = 2 GW/cm 2) TII is dissociated by a two-photon process and the T1 fragment is detected state specifically. The yield of T1 6p 2P3/2 (TI*) is measured as a function of the dissociation wavelength (480 nm-540 nm). If the dissociation wavelength is close to two-photon transitions of the T1 atom from 6p 2P3/2 to np 2p1/2,3/2 or mf 2F5/2,7/2, l,~= 10 ... 15, m=7 ... 12 dips in the yield are observed. These dips show a significant asymmetric broadening, compared to a free atomic transition and the observation is interpreted as an absorption process of the transient state of dissociating TII during the laser pulse. By applying the Landau-Zener approximation for the potential crossing of dressed molecular states, we are able to describe the broadening and the power density dependence of the observations. Simulations show that the asymmetry is determined by the difference potential of the electronic states which are coupled by the laser field.

Quasi-stationary detection of transient absorption of a dissociating molecule

“…Preliminary experiments on dissociation to Rydberg levels show large variations of the asymmetry and also transient two-photon absorption [8] was detected. Signals corresponding to the half collision of laser induced collisional energy transfer (LICET experiment [5]) were already observed in TtI exciting I.…”

“…In our recent paper [8] on absorption during dissociation we used the Landau-Zener approximation [22,23] to calculate the transition probability for a passage through the crossing region. This approach is also possible in the present situation by replacing 2h~o by hco in all expressions of [8] and noting that we now observe 1-PLz, the probability of a passage with a change of the electronic state.…”

“…In our recent experiments on two-photon absorption of dissociating TII [8] it was not possible for us to distinguish experimentally between the dissociation step and the absorption during dissociation~ because both processes were induced by the same laser pulse. In our new investigation we present a two-color experiment with onephoton absorption during dissociation in which we succeeded to distinguish between the initiation of the dissociation and the absorption during dissociation.…”