scholarly journals Gerade/ungerade symmetry-breaking in HD at the n = 2 dissociation limit

2000 ◽  
Vol 78 (5-6) ◽  
pp. 567-578 ◽  
Author(s):  
A de Lange ◽  
E Reinhold ◽  
W Hogervorst ◽  
W Ubachs
Keyword(s):  
Binding Energy ◽  
Symmetry Breaking ◽  
Extreme Ultraviolet ◽  
Dissociation Limit ◽  
Pulsed Lasers ◽  
Excitation Scheme ◽  
Empirical Potential ◽  
Vibrational Levels ◽  
Infrared Excitation ◽  
Semi Empirical

We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of [Formula: see text] 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of [Formula: see text]1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w

scholarly journals Gerade-ungerade symmetry breaking in HD: States close to N=2 dissociation limit

2008 ◽  
Vol 6 (1) ◽  
pp. 29-40
Author(s):  
Tasko Grozdanov
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Symmetry Breaking ◽  
Excellent Agreement ◽  
Bound States ◽  
Electronic States ◽  
Dissociation Limit ◽  
Empirical Potential ◽  
Oppenheimer Approximation ◽  
Semi Empirical

We review the consequences of the gerade-ungerade symmetry breaking in HD molecule. A particular attention is devoted to electronic states close to n=2 dissociation limit. The effects of the breakdown of the Born-Oppenheimer approximation are discussed. For the description of the molecular dynamics the formulation of the coupled-sates method is given. The method is applied to calculations of loosely bound states in the outer well of the II'1?g potential. The results are in excellent agreement with experimental data and calculations based on a semi-empirical potential.

Universal origin of heavy elements

2021 ◽  
Author(s):  
Jose Orce ◽  
Balaram Dey ◽  
Cebo Ngwetsheni ◽  
Brenden Lesch ◽  
Andile Zulu ◽  
...  
Keyword(s):  
Binding Energy ◽  
Symmetry Energy ◽  
Neutron Capture ◽  
Decay Rates ◽  
Heavy Elements ◽  
Capture Process ◽  
Atomic Nuclei ◽  
Radiative Neutron ◽  
Radiative Neutron Capture ◽  
Semi Empirical

Abstract The abundance of heavy elements above iron through the rapid neutron capture process or r-process is intimately related to the competition between neutron capture and $\beta$ decay rates, which ultimately depends on the binding energy of atomic nuclei. The well-known Bethe-Weizsacker semi-empirical mass formula describes the binding energy of ground states in nuclei with temperatures of T~0 MeV, where the nuclear symmetry energy saturates between 23-26 MeV. Here we find a larger saturation energy of ~30 MeV for nuclei at T~0.7-1.3 MeV, which corresponds to the typical temperatures where seed elements are created during the cooling down of the ejecta following neutron-star mergers and collapsars. This large symmetry energy yields a reduction of the binding energy per nucleon for neutron-rich nuclei; hence, the close in of the neutron dripline, where nuclei become unbound. This finding constrains exotic paths in the nucleosynthesis of heavy elements -- as supported by microscopic calculations of radiative neutron-capture rates -- and further supports the universal origin of heavy elements, as inferred from the abundances in extremely metal-poor stars and meteorites.

scholarly journals Coupled Nuclear-Electronic Decay Dynamics of O2 Inner Valence Excited States Revealed by Attosecond XUV Wave-Mixing Spectroscopy

2020 ◽  
Author(s):  
Yen-Cheng Lin ◽  
Ashley Fidler ◽  
Arvinder Sandhu ◽  
Robert R. Lucchese ◽  
C. William McCurdy ◽  
...  
Keyword(s):  
Rydberg State ◽  
Extreme Ultraviolet ◽  
Strong Dependence ◽  
Model Systems ◽  
Theoretical Treatment ◽  
Wave Mixing ◽  
Rydberg Series ◽  
Transient Wave ◽  
Decay Channels ◽  
Vibrational Levels

Multiple Rydberg series converging to the O<sub>2</sub><sup>+</sup> 𝑐 <sup>4</sup>Σ<sub>𝑢</sub><sup>−</sup> state, accessed by 20-25 eV extreme ultraviolet (XUV) light, serve as important model systems for the competition between nuclear dissociation and electronic autoionization. The dynamics of the lowest member of these series, the <i>3sσg</i> state around 21 eV, has been challenging to study owing to its ultra-short lifetime (< 10 fs). Here, we apply transient wave-mixing spectroscopy with an attosecond XUV pulse to investigate the decay dynamics of this electronic state. Lifetimes of 5.8±0.5 fs and 4.5±0.7 fs at 95% confidence intervals are obtained for v=0 and v=1 vibrational levels of the 3s Rydberg state, respectively. A theoretical treatment of predissociation and electronic autoionization finds that these lifetimes are dominated by electronic autoionization. The strong dependence of the electronic autoionization rate on the internuclear distance because of two ionic decay channels that cross the <i>3s</i> Rydberg state results in the different lifetimes of the two vibrational levels. The calculated lifetimes are highly sensitive to the location of the <i>3s</i> potential with respect to the decay channels; by slight adjustment of the location, values of 6.2 and 5.0 fs are obtained computationally for the v=0 and v=1 levels, respectively, in good agreement with experiment. Overall, an intriguing picture of the coupled nuclear-electronic dynamics is revealed by attosecond XUV wave-mixing spectroscopy, indicating that the decay dynamics are not a simple competition between isolated autoionization and predissociation processes.

THE LYMAN BANDS OF MOLECULAR HYDROGEN

1959 ◽  
Vol 37 (5) ◽  
pp. 636-659 ◽  
Author(s):  
G. Herzberg ◽  
L. L. Howe
Keyword(s):  
High Resolution ◽  
Vibrational Level ◽  
Ground State ◽  
Molecular Hydrogen ◽  
Equilibrium Constants ◽  
Dissociation Limit ◽  
Vibrational Levels ◽  
State Formula ◽  
Single Formula ◽  
Vibrational Constants

The Lyman bands of H2 have been investigated under high resolution with a view to improving the rotational and vibrational constants of H2 in its ground state. Precise Bv and ΔG values have been obtained for all vibrational levels of the ground state. One or two of the highest rotational levels of the last vibrational level (v = 14) lie above the dissociation limit. Both the [Formula: see text] and ΔG″ curves have a point of inflection at about v″ = 3. This makes it difficult to represent the whole course of each of these curves by a single formula and therefore makes the resulting equilibrium constants somewhat uncertain. This uncertainty is not very great for the rotational constants for which we find[Formula: see text]but is considerable for the vibrational constants ωe and ωexe for which three-, four-, five-, and six-term formulae give results diverging by ± 1 cm−1. The rotational and vibrational constants for the upper state [Formula: see text] of the Lyman bands are also determined. An appreciable correction to the position of the upper state is found.

The melting transition of Ni7 and Ni7H as modeled by a semi-empirical potential

1998 ◽  
Vol 295 (4) ◽  
pp. 366-372 ◽  
Author(s):  
E Curotto ◽  
David L Freeman ◽  
Bin Chen ◽  
J.D Doll
Keyword(s):  
Melting Transition ◽  
Empirical Potential ◽  
Semi Empirical

Semi-empirical formulae for Λ-binding energy in hypernuclei using mass distribution

Pramana ◽  
1997 ◽  
Vol 48 (5) ◽  
pp. 1027-1034 ◽  
Author(s):  
M Z Rahman Khan ◽  
Nasra Neelofer ◽  
M A Suhail
Keyword(s):  
Binding Energy ◽  
Mass Distribution ◽  
Semi Empirical
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