High-resolution photoelectron spectroscopy and calculations of the highest bound levels of ${{\rm{D}}}_{2}^{+}$ below the first dissociation threshold

Abstract

Pulsed-field ionization zero-kinetic-energy photoelectron spectra of D2 have been recorded from the intermediate H 1 Σ + g state to determine the positions of bound rovibronic levels of D + 2 located up to 1400 cm −1 below the D + + D(1s) dissociation threshold. The ion-pair character of the H intermediate state resulted in large changes ∆N = N + − N of the rotational quantum number upon photoionization, which enabled the observation of levels of D + 2 with rotational quantum number N + as high as 10. The experimental data cover a range of levels within which the usual hierarchy of timescales of the electronic, vibrational and rotational motions is inverted. The term values of these levels with respect to the X 1 Σ + g (v = 0, N = 0) rovibronic ground state of D2 and the energy intervals of the ionic states, measured with an accuracy of typically 0.11 cm −1 and 0.02 cm −1 , respectively, are compared with positions calculated ab-initio at various degrees of approximation, starting from the Born-Oppenheimer approximation and successively including adiabatic, nonadiabatic, relativistic and radiative corrections. The comparison shows that the accuracy of the photoelectron-spectroscopic measurement is sufficient to reveal the effects of the adiabatic, nonadiabatic, relativistic and radiative corrections on the absolute term values. Comparing our calculations, which rely on an approximate evaluation of the nonadiabatic corrections based on effective R-dependent reduced masses, with the theoretical results for N + ≤ 5 by Moss (J. Chem. Soc. Faraday Trans. 89, 3851 (1993)) and for N + ≤ 8 by Wolniewicz and Orlikowski (Mol. Phys. 74, 103 (1991)) enables the quantification of the errors introduced by our approximative treatment of the nonadiabatic corrections. Improved rotational term values of the H(v = 12) level were also derived.

Half-Collision Approach to Cold Chemistry: Shape Resonances, Elastic Scattering, and Radiative Association in the H++H and Beyer1, Merkt2 2018Phys. Rev. XSelf Cite

“…u first excited state. Beyer and Merkt [36] measured the positions of 65 bound states of the X þ 2 Σ þ g state with v þ ≥ 20, and of five of the seven bound levels of the A þ state and found good agreement with the results of Moss [34], Wolniewicz and Orlikowski [35], and their own calculations.…”

“…For the X þ state, nonadiabatic corrections are calculated approximately by using the R-dependent vibrational (μ vib ) and rotational (μ rot ) reduced masses reported by Jaquet [39], with which we obtain a closer agreement with the nonadiabatic energies determined for bound states by Moss [34] than with the reduced masses from Ref. [40] used in our previous study of D 2 [36]. Dissociation energies including relativistic and radiative corrections are determined by adding the terms hH rel i and hH rad i to the adiabatic potential curves as described in Ref.…”

“…The experiments were carried out using the equipment and methods described in Refs. [29,36]. A schematic representation of the experimental setup is depicted in Fig.…”

Metrology of high- n Rydberg states of molecular hydrogen with Δν/ν=2×10−10 accuracy

“…The measurement of Rydberg-Rydberg transitions at low frequencies is well suited to determine the rotational, fine and hyperfine intervals in molecular ions, but it is not suitable for the determination of vibrational intervals in the ion because of restrictions imposed by the Franck-Condon principle. Optical transitions from low-n intermediate states or from valence states, which have Born-Oppenheimer potential functions that differ from the potential function of the ion, allow access to Rydberg series converging on a very broad range of rovibronic levels of the molecular hydrogen ion [28][29][30], offering the prospect of measuring a wide range of rovibrational energy intervals of this ion.…”

Structure and dynamics of HD$^+$ in the vicinity of the H$^+$ + D and D$^+$ + H dissociation thresholds: Feshbach resonances and the role of g/u-symmetry breaking

“…The same laser system, consisting of a broadly tunable VUV laser used to drive the B-X transition, a visible laser to induce the H H-B and B B-B transitions, and a UV laser to access the dissociative-ionisation threshold, was already used to study the highest bound states and shape resonances of H + 2 and D + 2 and is described in Refs. [26,27,42,43]. The g/u-symmetry breaking in HD allowed the direct excitation, from the B 1 Σ + u (20 − 21, 1 − 4) intermediate levels, of rovibrational levels of the B B 1 Σ + u state [1,44], which has (1sσ g )3pσ u character in the inner well and (2pσ u )2sσ g and ion-pair character in the outer well.…”