Characterization of the 3dδ Rydberg state of MgAr+ using a quantum-control optical scheme

Abstract

We report a spectroscopic investigation of the 3dδ ( = 3 2 , 5 2 ) Rydberg states of the MgAr + molecular cation. Vibrational levels of the 3dδ 3/2 spin-orbit component with v 15 were observed to directly predissociate into charge-transfer continua correlating to the Mg(3s 2 1 S) + Ar + (3p 5 2 P) dissociation limit, making it possible to record their spectra by isolated-core multiphoton Rydberg dissociation spectroscopy. Vibrational states below v = 15, which do not predissociate, were characterized with partial rotational resolution using a multiphoton excitation and dissociation quantum-control scheme that radiatively couples the 3dδ vibronic states to predissociative levels of the 3dπ state. An effective Hamiltonian approach was used to theoretically investigate this scheme, including the origin of the control over the spectral lineshapes provided by the laser detuning. This approach provided results in quantitative agreement with the measured spectra. Potential-energy functions were derived for the 3dδ states from experimental data. They are very similar to the one of the X 2+ 1 + ground state of the MgAr 2+ doubly charged ion, highlighting the Rydberg character of the 3dδ state. Whereas homogeneous charge-transfer interactions play a major role in the dynamics of the Rydberg states of molecular ions, the present study shows that heterogeneous interactions leave these states essentially unaffected.

Characterization of the electronic ground state of Mg$_2^+$ by PFI-ZEKE photoelectron spectroscopy

“…The present work opens the possibility to study electronically excited states of Mg + 2 , and in particular its Rydberg states, by isolated-core multiphoton Rydberg dissociation [37]. The structure and dynamics of these states are expected to differ from the Rydberg states of MgAr + , which is one of the few molecular ions for which the Rydberg states are well characterized [38][39][40][41][42]. In the case of MgAr + , the ground state of the doubly charged ion (MgAr 2+ ) to which the Rydberg series converge is thermodynamically stable [42].…”

“…The knowledge of the ground electronic state of Mg + 2 is also required as a starting point to study the electronically excited states of the ion, and in particular the Rydberg series converging to the metastable levels of the Mg 2+ 2 ion [36], which have not been observed so far. We plan to study these states following the procedure we used recently to characterize the ground electronic state of MgAr 2+ and the Rydberg series of MgAr + converging to this doubly charged ion [37][38][39][40][41][42].…”

High-Resolution Photoelectron Spectroscopy of the Ground and First Excited Electronic States of MgXe+

“…The potential-energy function of the X + 2 Σ + state of MgXe + was determined from the vibrational structure of the PFI-ZEKE-PE spectrum in a least-squares fit. We calculated the vibrational term values by numerically solving the Schrödinger equation for the nuclear motion using a potential-energy function of the form 40 following the same procedure as in our studies of MgAr + , 15 , 39 MgKr + , 27 and MgNe + . 9 The potential-energy function in eq 1 comprises an attractive and a repulsive short-range interaction term and a long-range interaction term u LR ( R ).…”

“…following the same procedure as in our studies of MgAr + , 15,39 MgKr + , 27 and MgNe + . 9 The potential-energy function in eq 1 comprises an attractive and a repulsive short-range interaction term and a long-range interaction term u LR (R).…”

“…At large internuclear separation, these states can be regarded as the lowest members of the Rydberg series converging to low electronic states of the doubly charged MgXe 2+ . The first state in Mg−Rg + molecules with a potential-energy function similar to the potential-energy function of the ground state of the doubly charged ion is the 3dδ state, 15 corresponding to Mulliken's rule of the absence of a precursor orbital of the corresponding symmetry in the ion core. 16 The ground X 1 Σ + and metastable a 3 Π 0 states, as well as other low-lying electronically excited states of MgXe, were investigated in detail by Breckenridge and co-workers.…”