Accurate Experimental Determination of Bond Angle Distribution in Molecules

The Coulomb Explosion Imaging is an experimental technique which provides images of the fully correlated nuclear configuration within small molecules. The method is model independent and applicable to rigid and floppy molecules alike. Combining the techniques of Coulomb Explosion Imaging (CEI) and storage ring, allows to probe both the structure and the relaxation dynamics of molecular ions. Analysis of the decaying states enables to isolate the ground vibrational state from the excited states. This yields accurate results which can be compared directly to theory. This scheme has been exploited for the measurements of bond angle distributions in Quasi-Linear molecular ions, namely NH+ ND+ and CH+. Such species have been previously measured spectroscopically from which adiabatic potential surfaces were calculated. Molecular wave functions were extracted from these calculations, thus allowing predictions regarding the unobserved molecular structure. Being able to measure the molecular nuclear structure we hereby supply unique complimentary data describing the nuclear configuration distribution within the molecules measured and compare the measurement to the theoretical predictions. The comparison of the measured ground state angular distribution with present theories, reveal apparent large non-adiabatic contributions to the low-lying wave functions of NH+ ND+ and CH+