Rotation/Torsion Coupling in H5+, D5+, H4D+, and HD4+ Using Diffusion Monte Carlo

Marlett, Melanie; Lin, Zhou; McCoy, Anne B.

doi:10.1021/acs.jpca.5b05773

Cited by 14 publications

(8 citation statements)

References 33 publications

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“…The fact that the spectrum does not change when the value of the torsion angle is shifted from 90 to 0° suggests that, while the torsion is indeed large amplitude, its motion is nearly completely decoupled from the other vibrations considered in this study. This is consistent with the results of earlier work using DMC …”

Section: Resultssupporting

confidence: 94%

The Role of Tunneling in the Spectra of H₅⁺ and D₅⁺ up to 7300 cm^–1

et al. 2020

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The spectra for H5 + and D5 + are extended to cover the region between 4830 and 7300 cm–1. These spectra are obtained using mass-selected photodissociation spectroscopy. To understand the nature of the states that are accessed by the transitions in this and prior studies, we develop a four-dimensional model Hamiltonian. This Hamiltonian is expressed in terms of the two outer H2 stretches, the displacement of the shared proton from the center of mass of these two H2 groups, and the distance between the H2 groups. This choice is motivated by the large oscillator strength associated with the shared proton stretch and the fact that the spectral regions that have been probed correspond to zero, one, and two quanta of excitation in the H2 stretches. This model is analyzed using an adiabatic separation of the H2 stretches from the other two vibrations and includes the non-adiabatic couplings between H2 stretch states with the same total number of quanta of excitation in the H2 stretches. Based on the analysis of the energies and wave functions obtained from this model, we find that when there are one or more quanta of excitation in the H2 stretches the states come in pairs that reflect tunneling doublets. The states accessed by the transitions in the spectrum with the largest intensity are assigned to the members of the doublets with requisite symmetry that are localized on the lowest-energy adiabat for a given level of H2 excitation.

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Section: Resultssupporting

confidence: 94%

The Role of Tunneling in the Spectra of H₅⁺ and D₅⁺ up to 7300 cm^–1

et al. 2020

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“…The computations showed that H + 5 has a peculiar rotational-vibrational energy level structure, classifying this molecule as a prototypical astructural molecule. Marlett et al 35 confirmed this assessment and extended the DMC computations to rovibrational states of D + 5 , H 4 D + , and HD + 4 . As to experiments, in 2010 Cheng et al 37 reported experimental infrared spectra in the 2000-4500 cm −1 region.…”

Section: Reference Structure Bmentioning

confidence: 76%

“…The rotational energy levels utilized differ substantially from those of later, more elaborate studies. 8,35 Previous efforts 7,8 in our laboratory were carried out to compute and understand the rotational-vibrational energy level structure of H + 5 . The computations showed that H + 5 has a peculiar rotational-vibrational energy level structure, classifying this molecule as a prototypical astructural molecule.…”

Section: Reference Structure Bmentioning

confidence: 99%

“…During the last decade, based partially on the relatively accurate (semi)global ab initio PES available, 20,21 a number of theoretical 7,8,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and experimental 37,38 studies were carried out to characterize the vibrational dynamics of the H + 5 molecular ion as well as some of its deuterated isotopologues.…”

Section: Introductionmentioning

confidence: 99%

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Interpretation of the vibrational energy level structure of the astructural molecular ion H5+ and all of its deuterated isotopomers

Sarka

Császár

2016

The Journal of Chemical Physics

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Variational nuclear motion computations, employing an exact kinetic energy operator and two different potential energy surfaces, are performed to study the first 60 vibrational states of the molecular ion H5 (+)≡ [H2-H-H2](+) and all of its deuterated isotopologues and isotopomers, altogether 12 species. Detailed investigation of the vibrational wavefunctions mostly results in physically intuitive labels not only for the fundamentals but also for the overtone and combination states computed. The torsional motion associated with the left and right diatomics appears to be well separated from the other vibrational degrees of freedom for all species. The unusual structure of the higher-lying bending states and the heavy mixing of the internal motions is partly due to the astructural character of all these molecular ions. The existence of distinct isotopomers in the H5-nDn (+), n = 1-4 cases, in the energy range studied, is confirmed. Two rules determine the stability order of the isotopomers: first, when possible, H prefers to stay in the middle of the ions rather than at the sides, and, second, the isotopomer with a homonuclear diatomic at the side is always lower in energy. The large number of precise vibrational energies of the present study, as well as the detailed assignment of the states, should serve as benchmarks for future studies by more approximate nuclear-motion treatments, such as diffusion Monte Carlo and multiconfiguration time-dependent Hartree.

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“…In particular, on the vibrationally averaged PES the ∼60 cm −1 electronic barrier, hindering the proton hopping motion between the two sides, disappears, resulting in no difference in the “left” and “right” H 2 units for H