Double Resonance Spectroscopy of the B″B̅ 1Σu+ State of H2

Double resonance spectroscopy via the EF (1)Sigma(+)(g),nu\u27(EF)=6,J(\u27) state has been used to probe the rovibrational structure of the ungerade double-well B-n(B) over bar (1)Sigma(+)(u) state of H-2. Transitions to the B-n(B) over bar (1)Sigma(+)(u),nu((B) over bar)=17-35,J=0-4 levels of the outer-well and to the nu(n)(B)((B) over bar)=46-50,J=0-4 levels of the combined inner and outer wells above the barrier have been recorded by detecting both molecular and atomic ion production as a function of energy by using a time of flight mass spectrometer. Theoretical energy calculations incorporating the most recent potential curves have been used to aid in the assignment of observed transitions. Over 70 new rovibrational term energies are reported. Where comparisons are possible, good agreement is observed between the experimental measurements reported here and those of previous measurements. While significant perturbations are observed in the energy region above the double-well barrier, assignments to states with dominant inner and outer-well characteristics can still be made. Distinct dynamical behaviors of the levels below, at, and above the barrier have also been observed

Observations of the high vibrational levels of the B′′B̄ 1Σ+u state of H2

Double-resonance laser spectroscopy via the E F 1Σ+g, v\u27 = 6, J\u27 = 0–2 state was used to probe the high vibrational levels of the B′′B̄ 1Σ+u state of molecular hydrogen. Resonantly enhanced multiphotonionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v = 51–66 levels for the B00B ̄ state of H2 are reported, which, taken with previous results, span the v = 46–69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spectrosc. 238, 118–126 (2006)]. The average difference between the 84 measured energies and calculated energies is 3.8 cm–1 with a standard deviation of 5.3 cm–1. This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the 1Σu+ and 1Πu+ states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit

Observations of the high vibrational levels of the B′′B̄ 1Σu+ state of H2

Double-resonance laser spectroscopy via the E F 1Σg+, v\u27=6, J\u27=0-2 state was used to probe the high vibrational levels of the B B-bar 1Σu+ state of molecular hydrogen. Resonantly-enhanced multiphoton ionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v=51-66 levels for the B B-bar state of H2 are reported, which, taken with previous results, span the v=46-69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spec. 238, 118 (2006)]. The average difference between the 84 measured energies and calculated energies is -3.8 cm-1 with a standard deviation of 5.3 cm-1. This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the 1Σu+ and 1Πu+ states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit

Observations of the high vibrational levels of the B′′B̄ 1Σu+ state of H2

Double-resonance laser spectroscopy via the E F 1Σg+, v\u27=6, J\u27=0-2 state was used to probe the high vibrational levels of the B B-bar 1Σu+ state of molecular hydrogen. Resonantly-enhanced multiphoton ionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v=51-66 levels for the B B-bar state of H2 are reported, which, taken with previous results, span the v=46-69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spec. 238, 118 (2006)]. The average difference between the 84 measured energies and calculated energies is -3.8 cm-1 with a standard deviation of 5.3 cm-1. This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the 1Σu+ and 1Πu+ states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit

Observations of the high vibrational levels of the B′′B̄ 1Σ+u state of H2

Double-resonance laser spectroscopy via the E F 1Σ+g, v\u27 = 6, J\u27 = 0–2 state was used to probe the high vibrational levels of the B′′B̄ 1Σ+u state of molecular hydrogen. Resonantly enhanced multiphotonionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v = 51–66 levels for the B00B ̄ state of H2 are reported, which, taken with previous results, span the v = 46–69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spectrosc. 238, 118–126 (2006)]. The average difference between the 84 measured energies and calculated energies is 3.8 cm–1 with a standard deviation of 5.3 cm–1. This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the 1Σu+ and 1Πu+ states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit

Double resonance spectroscopy of the D1Πu+ and B\u27\u27B-bar 1Σu+ states near the third dissociation threshold of H2

Double-resonance laser spectroscopy via the E, F 1Σg+, v\u27 = 6, J\u27 state was used to probe the energy region below the third dissociation limit of molecular hydrogen. Resonantly enhanced multi-photon ionization spectra were recorded by detecting ion production as a function of energy using a time-of-flight mass spectrometer. Energies and line widths for the v = 14–17 levels of the D1Πu+ state of H2 are reported and compared to experimental data obtained by using VUV synchrotron light excitation (Dickenson et al. 2010 J. Chem. Phys. 133 144317) and fully ab initio non-adiabatic calculations of D1Πu+ state energies and line widths (Glass-Maujean et al. 2012 Phys. Rev. A 86 052507). Several high vibrational levels of the B\u27\u27B-bar 1Σu+ state were also observed in this region. Term energies and rotational constants for the v = 67–69 vibrational levels are reported and compared to highly accurate ro-vibrational energy level predictions from fully ab initio non-adiabatic calculations of the first six 1Σu+ levels of H2 (Wolniewicz et al 2006 J. Mol. Spectrosc. 238 118). While additional observed transitions can be assigned to other states, several unassigned features in the spectra highlight the need for a fully integrated theoretical treatment of dissociation and ionization to understand the complex pattern of highly vibrationally excited states expected in this region

Double resonance spectroscopy of the D1Πu+ and B\u27\u27B-bar 1Σu+ states near the third dissociation threshold of H2

Double-resonance laser spectroscopy via the E, F 1Σg+, v\u27 = 6, J\u27 state was used to probe the energy region below the third dissociation limit of molecular hydrogen. Resonantly enhanced multi-photon ionization spectra were recorded by detecting ion production as a function of energy using a time-of-flight mass spectrometer. Energies and line widths for the v = 14–17 levels of the D1Πu+ state of H2 are reported and compared to experimental data obtained by using VUV synchrotron light excitation (Dickenson et al. 2010 J. Chem. Phys. 133 144317) and fully ab initio non-adiabatic calculations of D1Πu+ state energies and line widths (Glass-Maujean et al. 2012 Phys. Rev. A 86 052507). Several high vibrational levels of the B\u27\u27B-bar 1Σu+ state were also observed in this region. Term energies and rotational constants for the v = 67–69 vibrational levels are reported and compared to highly accurate ro-vibrational energy level predictions from fully ab initio non-adiabatic calculations of the first six 1Σu+ levels of H2 (Wolniewicz et al 2006 J. Mol. Spectrosc. 238 118). While additional observed transitions can be assigned to other states, several unassigned features in the spectra highlight the need for a fully integrated theoretical treatment of dissociation and ionization to understand the complex pattern of highly vibrationally excited states expected in this region