Determinations of some hydrogen molecular constants

Foltz, J. V.; Rank, D. H.; Wiggins, T. A.

doi:10.1016/0022-2852(66)90138-x

Cited by 93 publications

(29 citation statements)

References 16 publications

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“…Dissociation spectrum ofpara-Ht ( J"= 0) level J"=0, the first rotational term value, namely, F"(1)=118.49 cm ' [18], was added, giving DL (Hz}=118377.06+0.04 cm '. (The estimate obtained from the spectrum of para-H2 agrees with this value. )…”

Section: Results and Analysismentioning

confidence: 99%

Dissociation energies of the hydrogen and deuterium molecules

1994

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Fluorescence-excitation spectroscopy near -84 nm has been used to measure the threshold for the dissociation of H~{B' 'X"+ ) =H{1s)+H(2s) at 118377.06+0.04 cm ' and the corresponding limit for D2 at 119029.72+0.04 cm '. The onset of dissociation was observed clearly, free from overlapping molecular lines, by the use of delayed quenching of 2s atoms produced by the photoexcitation pulse. These measurements have yielded the values Do(H2)=36118. 11+0. 08 cm ' and Do(D2)=36748. 38+0.07 cm ' for the dissociation energies of the ground electronic states X 'Xg+, in agreement with the latest ab initio calculations, which include nonadiabatic, relativistic, and radiative corrections. From the present values and recently determined ionization energies of H& and D&, the dissociation energies of the respective ions were found to be Do(H2+)=21379. 37+0.08 cm ' and Do(D2+)=21711.64+0.07 cm ', also in agreement with recent ab initio calculations.PACS number(s): 35.20.6s, 33.20.Ni, 32.50.+d

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Section: Results and Analysismentioning

confidence: 99%

Dissociation energies of the hydrogen and deuterium molecules

1994

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“…Since the first measurements of the quadrupole spectra of H 2 overtone bands by Herzberg [38] using long-path classical absorption techniques, refinements have been applied through the years, e.g. by using more accurate echelle spectrometers by Rank and co-workers [39,40,73]. The improvements continued in the study of Bragg et al [41] who employed Fourier-Transform (FT) spectroscopy techniques.…”

Section: Comparison To Previous Studiesmentioning

confidence: 96%

“…Experimental data included in the fit came from Dabrowski [50] for Lyman and Werner band transitions, but also most ground state studies mentioned above [40,75,80,83,85,91]. Similar global fitting analyses based on the Dunham relation was also performed by the same group for HD [71] and D 2 [72] resulting in similar uncertainties as in the case of H 2 .…”

Section: Comparison To Previous Studiesmentioning

confidence: 98%

“…Herzberg first predicted, in 1938, that it should be possible to record rovibrational transitions in the ground state manifold [37], and later discovered the quadrupole spectrum in 1949 by photographing a total of eight lines in the (2,0) and (3,0) bands [38]. Subsequently the quadrupole spectrum including the fundamental (1,0) band was investigated by several other groups, for example by Rank and co-workers [39,40]. The measurements by Bragg et al [41] greatly improved the accuracy of the spectroscopy of the quadrupole bands and was until recent years considered as the most accurate work on the direct measurement of the vibrational splittings.…”

Section: Introductionmentioning

confidence: 99%

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VUV-synchrotron absorption studies of N2 and CO at 900K

Niu

Heays

Jones

et al. 2015

Journal of Molecular Spectroscopy

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“…5 We have considered a static lattice with c / a = ͱ 8 / 3, and rotational constants of the isolated molecule. 25 The quantities ͑c͒ are negligible with respect to the two "roton" terms ͑r 1 ͒ and ͑r 2 ͒ , that are large and have opposite sign. It is interesting to note that the main effect of the three-body terms is that of uniformly shifting the lines of the triplet, which hardly affects the splitting.…”

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confidence: 99%

Importance of anisotropic three-body forces in solid hydrogen

Moraldi

Ulivi²

2006

Phys. Rev. B

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We take into account three-body anisotropic forces between molecules to calculate the energy of the S 0 ͑0͒ triplet in solid hexagonal close packed hydrogen under pressure. Three-body contributions result in one term depending on the orientation of only one molecule ͑crystal field term͒ and two others that couple rotations of different molecules ͑roton terms͒. Three-body interactions contribute, to a large extent, to the roton frequencies. Their inclusion in the calculation increases the calculated average frequency of the triplet, even at relatively low density, changing substantially the estimate of the internuclear distance. By contrast, the triplet splitting is substantially unaffected by three-body terms, resulting therefore a good candidate to test anisotropic two-body potential models against experiment.The structure and the dynamical properties of solid hydrogen under pressure are exciting subjects of active research. [1][2][3][4][5][6] In the low-pressure hexagonal close-packed ͑hcp͒ phase, the molecules rotate in their lattice sites and J is a good quantum number. In an ordered crystal ͑with only para-H 2 molecules͒, the rotational excitation acquires a collective character, due to the anisotropic interaction between molecules. The transition from the ground state ͑all molecules in the J = 0 state͒ to the state with one J = 2 excitation gives rise, in the Raman spectrum, to the S 0 ͑0͒ triplet, that has been observed experimentally at low pressure 7 and up to about 110 GPa. 4,[8][9][10] Above this pressure, solid para-hydrogen transforms to an orientationally ordered phase ͓broken symmetry phase ͑BSP͔͒, whose crystal structure has been investigated theoretically, 11-13 spectroscopically, 3 and, recently, with more direct methods as x-rays and neutron scattering. 6 Values of the S 0 ͑0͒ Raman frequencies and of their pressure evolution contain information on the same anisotropic intermolecular potential components which drive the transition to the BSP.The quantitative analysis of these data by theories based on known anisotropic pair potentials is extremely problematical and is far from being satisfactory. 4,14 One problem concerns the splitting of the triplet which is always overestimated, as underestimated is the transition pressure to the BSP, if calculated analogously. The other quantity of importance is the average position of the triplet, which depends on the rotational constant and therefore gives information on the intramolecular distance and on its pressure dependence. The information extracted with the analysis of the Raman data depends, however, on our capability to calculate the contribution of the anisotropic potential to the roton energies ͑average value and splitting͒ in the solid. The main contribution to the splitting comes from the electric quadrupolequadrupole interaction, and is generally calculated within first-order perturbation theory. 1 Three other contributions may have importance at high pressure: One comes from different components of the anisotropic pair-wise potential, one fr...

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Determinations of some hydrogen molecular constants

Cited by 93 publications

References 16 publications

Dissociation energies of the hydrogen and deuterium molecules

Dissociation energies of the hydrogen and deuterium molecules

VUV-synchrotron absorption studies of N2 and CO at 900K

Importance of anisotropic three-body forces in solid hydrogen

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