Precision measurements and test of molecular theory in highly excited vibrational states of H2 (v = 11)

Abstract

Accurate EF 1 Σ + g − X 1 Σ + g transition energies in molecular hydrogen were determined for transitions originating from levels with highly-excited vibrational quantum number, v = 11, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited H * 2 , produced via the photodissociation of H 2 S, yielding transition frequencies with accuracies of 45 MHz or 0.0015 cm −1 . An important improvement is the enhanced detection efficiency by resonant excitation to autoionizing 7pπ electronic Rydberg states, resulting in narrow transitions due to reduced ac-Stark effects. Using known EF level energies, the level energies of X(v = 11, J = 1, 3 − 5) states are derived with accuracies of typically 0.002 cm −1 . These experimental values are in excellent agreement with, and are more accurate than the results obtained from the most advanced ab initio molecular theory calculations including relativistic and QED contributions.

Deep-Ultraviolet Frequency Metrology of H2 for Tests of Molecular Quantum Theory

“…Although the increased complexity of the electronic structure and the additional vibrational and rotational degrees of freedom impose serious theoretical and experimental challenges, it also provides additional opportunities to explore new physics. Measurements of various level energies [5][6][7][8][9][10] are in excellent agreement with the most recent theoretical predictions [11][12][13]. Comparisons between the experimental results and theory provide constraints on possible physics beyond the standard model, such as hypothetical fifth forces and extra dimensions [14][15][16][17].…”

Excitation of H2 at large internuclear separation: outer well states and continuum resonances

“…This difficulty was overcome in the subsequent study of X(v = 11) levels, where a resonant ionisation detection scheme followed by H + 2 detection was implemented. This led to symmetric and narrower line profiles limited only by the instrumental bandwidth [29]. The latter method is followed in the present study.…”

“…The present study builds on the methods and previous measurement of Q (1), Q(3), Q(4) and Q(5) two-photon lines in the F − X(0, 11) band [29]. In that study the line identification was based on the accurately reported level energies of F(v = 0, J ) [26] and the calculated X(v = 11, J ) levels [31].…”

“…F 1 + g outer-well states. In subsequent investigations, exploring this photolysis pathway in a more refined manner using three independently tunable lasers [28,29], the identification of F 1 + g -X 1 + g two-photon transitions was based on the known energy separations between the F and X levels. Accurate knowledge of the X 1 + g (v, J ) levels is obtained from advanced ab initio calculations [30,31], while the level energies in F 1 + g are derived from Bailly et al [26].…”

Isotope dependence of thec3Πu−b3Σ${}_{u}^{+}$ andD1Π${}_{u}^{+}$−B′1Σ${}_{u}^{+}$ predissociation rates of molecular hydrogen

“…The effect of the coupling with other states is treated as a small non-adiabatic correction (Wolniewicz 1993, 1995, Pachucki and Komasa 2015. When relativistic (Puchalski et al 2017) and radiative (Piszczatowski et al 2009, Puchalski et al 2016 corrections are considered, the calculated and measured X g 1 S + energies agree within ∼0.001 cm −1 for low (v, J) levels and ∼0.005 cm −1 for high (v, J) levels (Komasa et al 2011, Pachucki and Komasa 2010, Niu et al 2014, Trivikram et al 2016, Cozijn et al 2018. Since excited states are not well-separated, the coupled Schrödinger equation method, usually for a few close low-lying states, is used (Senn et al 1988).…”