Communication: Test of quantum chemistry in vibrationally hot hydrogen molecules

Abstract

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The v = 12, J = 0 - 3 rovibrational levels of H2 (X(1)Σg (+)), lying only 2000 cm(-1) below the first dissociation limit, were populated by photodissociation of H2S and their level energies were accurately determined by two-photon Doppler-free spectroscopy. A comparison between the experimental results on v = 12 level energies with the best ab initio calculations shows a good agreement, where the present experimental accuracy of 3.5 × 10(-3) cm(-1) is more precise than theory, hence providing a gateway to further test theoretical advances in this benchmark quantum system.

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

“…The ionization laser source at 302-305 nm, from the frequency-doubled output of another PDL (also with rhodamine 640 dye), is used to resonantly excite from the EF to autoionizing Rydberg states to eventually form H + 2 ions. This 2 + 1 ′ resonance-enhanced multiphoton ionization (REMPI) scheme results in much improved sensitivities compared to our previous study [22].…”

“…The present study, targeting H 2 (v = 11) levels, is performed using the same experimental setup as in Ref. [22], depicted schematically in Fig. 1.…”

“…That study used a single powerful laser for dissociation, for subsequent H 2 spectroscopy, and to induce dissociative ionization for signal detection. Niu et al [22] utilized up to three separate laser sources to address the production, probe, and detection steps in a better controlled fashion. The present study, targeting H 2 (v = 11) levels, is performed using the same experimental setup as in Ref.…”

“…Recently, we reported a precision measurement on highly excited vibrational states in H 2 [22]. The experimental investigation of such highly excited vibrational states probes the region where the calculations of Komasa et al [9] are the least accurate, specifically in the v = 6-12 range.…”

“…[22] and that implement improvements, leading to a narrowing of the resonances. This is achieved by the use of a resonant ionization step to molecular Rydberg states, thereby enhancing the detection efficiency significantly.…”