High-resolution photoelectron spectroscopy of the ground and first excited electronic states of MgKr⁺

We report on the characterisation of the lowest three electronic states of MgKr+, the X+ (2)Sigma(+) ground state associated with the Mg+ (3s) S-2(1/2) + Kr(4p)(6) S-1(0) dissociation limit and the A(+) (2)Pi(Omega) (Omega = 1/2, 3/2) and B+ (2)Sigma(+) excited states associated with the Mg+ (3p) P-2(1/2,3/2) + Kr(4p)(6) S-1(0) dissociation limits. The vibrational structure of the X+ ground state was measured by pulsed-field-ionisation zero-kinetic-energy photoelectron spectroscopy starting from the a (3)Pi(0) metastable state of MgKr generated by laser ablation of a Mg rod in a Kr supersonic beam. The vibrational assignment was derived from the isotopic structure of the spectra and the adiabatic ionisation energy of the a -> X+ ionising transition was determined to be 38182.4(2.0) cm(-1). Partially rotationally resolved spectra of the A(+) <- X+ and B+ <- X+ transitions were recorded by monitoring the yield of Mg+ ions produced by dissociation of MgKr+ using the technique of isolated-core Rydberg-dissociation spectroscopy. Analytical potential-energy functions of the X+, A(+), and B+ states were derived using a global model of these states that includes the spin-orbit interaction. The observation of the highest vibrational levels of the B+ state and the onset of the Kr + Mg+ (3p) dissociation continuum enabled the precise determination of the dissociation energies of the X+, A(+) and B+ states of MgKr+ and of the a state of MgKr. The X+, A(+) and B+ states of MgKr+ are important stepping stones to access the Rydberg states of MgKr+ and the ground state of MgKr2+ by resonant multi photon excitation. [GRAPHICS] .