Fine and hyperfine structure in the a3II state of CH+

Spectroscopic and theoretical studies concerning the a3II state of CH+ are reviewed, with particular consideration given to the infrared predissociation spectrum of the ion. This spectrum is primarily due to vibration-rotation transitions of the a3II state involving v=5 to 12 and J=20 to 35. Some results of a spectral simulation, making use of a rotationally-adiabatic model, are presented to justify the proposed assignment. The nuclear-hyperfine structure of the observed transitions is studied in detail, with a new calculation of splittings presented. Some semi-quantitative conclusions can be drawn with reference to the variation of the Fermi Contact parameter, b, as a function of internuclear distance. © 1990 Akadémiai Kiadó

Applications of molecular Rydberg states in chemical dynamics and spectroscopy

Molecules in high Rydberg states, in which one electron has been excited into a hydrogenic orbital of large mean radius, have many unusual properties compared to ground state molecules. These properties, which are reviewed in this article, make them suitable for a diverse and growing number of applications in chemical dynamics. The most recent methods for studying molecular Rydberg states using high-resolution spectroscopy and theory, including effects of electric fields, are described here. An important feature is the high susceptibility of Rydberg states to external field perturbation which not only has a profound effect on the observable energy levels, spectroscopic intensities and lifetimes, but is also useful for state-selective detection through field ionization. The large dipole moment that can be created in a field is also useful for controlling the motion of molecules in Rydberg states. The applications reviewed here include: ZEKE (zero kinetic energy), MATI (mass-analyzed threshold ionization) and PIRI (photo-induced Rydberg ionization) spectroscopy; pulsed-field recombination of ions and electrons; the state selection and reaction of molecular ions; collisions of Rydberg states with neutrals, ions and metallic surfaces; Rydberg tagging and imaging of products of photodissociation; and the control of translational motion and orientation via the use of inhomogeneous fields

Demonstration of the combination of slice imaging and Rydberg tagging for studies of photodissociation dynamics.

The slice-imaging variant of photofragment ion imaging is combined with Rydberg tagging. The photodissociation of NO(2) at 355 nm is used as the test system and the NO fragments are Rydberg tagged by two-photon two-color excitation via the intermediate A (2)Sigma(+) state. Images obtained by this method are compared with ion images obtained in the same apparatus using the approach of Kitsopoulos and co-workers [Rev. Sci. Instrum. 72, 3848 (2001)]. Comparable resolution and angular distributions are obtained in the two cases. It is proposed that the method demonstrated here could provide a complementary approach to existing ion-imaging methods, especially where resonantly enhanced multiphoton ionization detection of fragments is problematic