Photolysis Production and Spectroscopic Investigation of the Highest Vibrational States in H₂ (X¹Σ_g⁺ v = 13, 14)

Abstract

Rovibrational quantum states in the X 1 Σ g + electronic ground state of H 2 are prepared in the v = 13 vibrational level up to its highest bound rotational level J = 7, and in the highest bound vibrational level v = 14 (for J = 1) by two-photon photolysis of H 2 S. These states are laser-excited in a subsequent two-photon scheme into F 1 Σ g + outer well states, where the assignment of the highest ( v , J ) states is derived from a comparison of experimentally known levels in F 1 Σ g + , combined with ab initio calculations of X 1 Σ g + levels. The assignments are further verified by excitation of F 1 Σ g + population into autoionizing continuum resonances, which are compared with multichannel quantum defect calculations. Precision spectroscopic measurements of the F-X intervals form a test for the ab initio calculations of ground state levels at high vibrational quantum numbers and large internuclear separations, for which agreement is found.

Rotational and nuclear-spin level dependent photodissociation dynamics of H2S

“…The H 2 products arising via the former route carry substantial vibrational but little rotational excitation. Previous REMPI studies have reported formation of H 2 products in high v ′′, low J ′′ states following excitation of H 2 S to similar total energies 46 – 50 . The P ( E T ) distributions measured when exciting parent levels with < J b 2 >> 0 reveal a rival Coriolis-induced pathway yielding additional H 2 products, characterised by little vibrational but massive rotational excitation—including population of super-rotor levels of H 2 .…”

Precision measurement of quasi-bound resonances in H$_2$ and the H + H scattering length

“…They assigned transitions between highvibrational states in H 2 to both inner and outer well states in the EF 1 Σ + g double well potential. However, in the controlled two and three-laser studies probing X(v = 11 − 14) [41][42][43][44] only transitions to the F 1 Σ + g outer well could be confirmed. In an alternative study, starting from the photolysis of H 2 CO, therewith producing H 2 vibrational states of intermediate quantum numbers X(v = 3 − 9), two-photon transitions to both EF 1 Σ + g inner and outer well were found [45].…”

“…The photolysis resonance at 291 nm was used for the production and investigation of H 2 molecules in v = 11 vibrational states [43]. For the production of H 2 in v = 13, 14 levels photolysis on the two-photon resonance at 281.8 nm was employed [44]. In the present experiment the wavelength of the dissociation laser is tuned to this two-photon absorption resonance in H 2 S at 281.8 nm, providing sufficient energy to overcome the dissociation energy, at 69935(25) cm −1 , for a complete three particle dissociation [53,54] with an excess of 1000 cm −1 above threshold.…”

“…In an alternative study, starting from the photolysis of H 2 CO, therewith producing H 2 vibrational states of intermediate quantum numbers X(v = 3 − 9), two-photon transitions to both EF 1 Σ + g inner and outer well were found [45]. Precision spectroscopic measurements probing the vibrational states just below the dissociation threshold allowed for tests of molecular ab initio calculations for these quantum states exhibiting wave function density at large internuclear separation [44].…”

“…The experimental setup, displayed in some detail in Fig. 1, is essentially similar to the one used previously for the detection of bound resonances below the dissociation threshold [42][43][44]. Two-photon UV-photolysis proceeds via the path:…”