Laser-induced Coulomb explosion imaging of alkali-metal dimers on helium nanodroplets
Résumé
Alkali-metal dimers, Ak 2 , residing on the surface of He nanodroplets, are doubly ionized due to multiphoton absorption from an intense 50-fs laser pulse leading to fragmentation into a pair of alkali-metal cations. Based on the measured kinetic energy distributions P(E kin) of the Ak + fragment ions, we retrieve the distribution of internuclear distances P(R) via the Ak 2+ 2 potential curve. Results are obtained for Na 2 , K 2 , Rb 2 , and Cs 2 in both the 1 1 g + ground state and the lowest-lying triplet state 1 3 u + and for Li 2 in the 1 3 u + state. For Li 2 , K 2 , and Rb 2 , the center of the measured P(R) is close to the center of the wave function (R) of the vibrational ground state in the 1 1 g + and 1 3 u + states, whereas for Na 2 and Cs 2 small shifts are observed. For all the Ak 2 , the width of the measured P(R) is broader than | (R)| 2 by a factor of 2-4. We discuss that resonance effects in the multiphoton ionization and interaction of the Ak + ion with the He droplet give rise to the observed deviations of P(R) from | (R)| 2. Despite these deviations, we deem that timed Coulomb explosion will allow imaging of vibrational wave packets in alkali-metal dimers on He droplets surfaces.
Domaines
Physique [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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