B. Gaire

Frustrated tunnelling ionization during strong-field fragmentation of D3+

We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D3+ to D+xa0+xa0D+xa0+xa0D with 1016xa0Wxa0cm−2, 790xa0nm, 40xa0fs (and 7xa0fs) laser pulses. This feature strongly mimics the behaviour of the D+xa0+xa0D+xa0+xa0D+ channel. From the experimental evidence, we conclude that the origin of the feature is due to frustrated tunnelling ionization, the first observation of this mechanism in a polyatomic system. Furthermore, we unravel evidence of frustrated tunnelling ionization in dissociation, both two-body breakup to Dxa0+xa0D2+ and D+xa0+xa0D2, and three-body breakup to D+xa0+xa0Dxa0+xa0D.

Elucidating isotopic effects in intense ultrafast laser-driven D2H+ fragmentation

The triatomic hydrogen molecular ion is instrumental as a benchmark towards understanding the strong-field dynamics of polyatomic molecules. Using a crossed-beams coincidence three-dimensional momentum imaging method, we demonstrate clear isotopic effects in the fragmentation of D2H+ induced by 7 fs (40 fs), 790?nm laser pulses at an intensity of 1016 W cm?2 (5 ? 1015 W cm?2). Our experiment uniquely separates all fragmentation channels and provides kinematically complete information for the nuclear fragments. For example, we show that for dissociative ionization of D2H+ there is a large difference in branching ratios of the two-body channels, namely, H++D dominates D++HD+, whereas there is minimal difference in branching ratios between the dissociation channels H++D2 and D++HD.

Permanent dipole transitions remain elusive in HD+ strong-field dissociation

A pertinent question in strong-field molecular physics is: what role does the permanent electric dipole moment of heteronuclear molecules play in their dissociation dynamics? Recently, Kiess et al (2008 Phys. Rev. A 77 053401) reported the first evidence for direct two-photon dissociation of an HD+ beam involving its permanent dipole moment, using 790 nm, 100 fs pulses. However, the measurement was convoluted by the fact that the H+ (H) and D+ (D) fragments could not be well resolved. Using high resolution coincidence 3D momentum imaging, which distinguishes all fragments, we find new evidence that challenges the previous findings. Specifically, we find that the small peak observed and assigned earlier to direct two-photon dissociation is instead due to one-photon dissociation of the v= 8 vibrational state by bond softening. Our vibrationally resolved spectra covering the intensity interval 3 × 1013 − 5 × 1014 W cm−2 show that one-photon dissociation of HD+ dominates, with no clear evidence of permanent dipole transitions.

Experimental measurement of Interatomic Coulombic Decay rates in Argon dimers

We present a method by which the internuclear distance-dependent decay width ᴦ(r) of Interatomic Coulombic Decay can be obtained using a measured energy distributions and a classical nuclear dynamics model.

A molecular movie of Interatomic Coulombic Decay in NeKr

Interatomic Coulombic Decay in mixed NeKr dimers has been measured time-resolved and the nuclear dynamics of the decay have been investigated.

Low kinetic energy release upon dissociation of benchmark molecular ions

We explore very slow laser-induced dissociation processes of molecular ion beams employing an upgraded coincidence 3D momentum imaging technique. A selection of our studies, focused on zero-photon dissociation of H2+, two-body breakup of D3+, and vibrational structure in O2+ dissociation, will be presented.