Matrix-isolation experiments near 3 K and state-of-the-art quantum chemical computations demonstrate that oxalic acid [1, (COOH)2] exhibits a sequential mechanical tunneling phenomenon not previously observed. Intensities of numerous infrared (IR) bands were used to monitor the temporal evolution lowest-energy O-H rotamers (1cTc, 1cTt, 1tTt) for up 19 days following near-infrared irradiation matrix. The relative energies these are 0.0 (1cTc), 2.6 (1cTt), 4.0 (1tTt) kcal mol(-1). A 1tTt →...

Spectra of vibrational overtone and combination bands from ground state were measured using an action spectroscopy technique with active background suppression in a cryogenic 22 pole radio frequency ion trap apparatus. Spectroscopic constants for the upper levels transitions determined band origins being 6846.77981(90) cm-1 (2ν1, NH stretch), 6640.47624(43) (ν1+ν2), 6282.03578(63) (2ν2, CH 6588.4894(20) (ν2+ν3+2ν50). State art ab initio VCI calculations up to 104cm-1 complement experimental data.

Variational nuclear motion computations, employing an exact kinetic energy operator and two different potential surfaces, are performed to study the first 60 vibrational states of molecular ion H5+≡ [H2–H–H2]+ all its deuterated isotopologues isotopomers, altogether 12 species. Detailed investigation wavefunctions mostly results in physically intuitive labels not only for fundamentals but also overtone combination computed. The torsional associated with left right diatomics appears be well...

Motivated by the energetic and environmental relevance of methane clathrates, highly accurate ab initio potential energy surfaces (PESs) have been developed for three possible dimers water molecules: (H2O)2, CH4·H2O, (CH4)2. While only a single monomer geometry was used each in calculations, PES parameterization makes it to produce distinct all isotopologues within rigid-monomer approximation. The PESs were fitted computations at frozen-core coupled-cluster level with single, double,...

ABSTRACT New MiZo line lists are presented for the D2H+ and D$_3^+$ isotopologues of H$_3^+$. These plus existing H$_3^+$ MiZATeP ST H2D+ updated using empirical energy levels generated marvel procedure H$_3^+$, H2D+, D2H+, effective Hamiltonian energies which there is significantly less laboratory data available. updates allow accurate frequencies far infrared lines these species to be predicted. Assignments extended a combination high accuracy variational calculations analysis transition...

The fourth-age quantum chemical code GENIUSH is used for the variational determination of rotational-vibrational energy levels corresponding to reduced- and full-dimensional models \documentclass[12pt]{minimal}\begin{document}${\rm H}_5^+$\end{document}H5+, a molecular ion exhibiting several strongly coupled large-amplitude motions. computations are supplemented with one- two-dimensional analytic results which help understand peculiar rovibrational energy-level structure computed correctly...

Rovibrational quantum nuclear motion computations, with J = 0, 1, and 2, are reported for the intermolecular degrees of freedom methane-water dimer, where is number describing overall rotation complex. The computations provide first explanation far-infrared spectrum this complex published in J. Chem. Phys., 1994, 100, 863. All experimentally rovibrational transitions, up to can be assigned transitions between theoretically computed levels. deviation experimental 0.5 cm(-1) ortho 2 para...

Rovibrational states of methane–water isotopologues are computed in a variational procedure and the wave functions analyzed terms rigid-rotor coupled-rotors models.

The variational nuclear-motion codes ElVibRot and GENIUSH have been used to compute rotational-vibrational states of the F(-)(H2O) anion its deuterated isotopologue, F(-)(D2O), employing a full-dimensional, semiglobal potential energy surface (PES) called SLBCL, developed as part this study for ground electronic state complex. PES is determined from all-electron, explicitly correlated coupled-cluster singles, doubles, connected triples [CCSD(T)-F12a] computations with an atom-centered,...

Rotational-vibrational states of the Ar·NO+ cationic complex are computed, below, above, and well above complex's first dissociation energy, using variational nuclear motion close-coupling scattering computations. The HSLH potential energy surface used in this study (J. Chem. Phys., 2011, 135, 044312) is characterized by a D0 = 887.0 cm-1 supports 200 bound vibrational states. bound-state energies corresponding wave functions allow interpretation scarcely available experimental results about...

Abstract The concept of quasistructural molecules is introduced. For (a) the notion a static equilibrium structure, corresponding to minimum on potential energy surface molecule, loses its strict meaning, (b) internal nuclear motions (rotations and vibrations) become dominant, resulting in an effective molecular structure often even qualitatively different from one, (c) separation breaks down, rotational vibrational degrees freedom cannot be separated each other when interpreting lowest...

One-dimensional (1D) and two-dimensional (2D) models are investigated, which help to understand the unusual rovibrational energy-level structure of astronomically relevant chemically interesting astructural molecular ion H+5. Due very low hindering barrier characterising 1D torsion-only vibrational model H+5, this yields strongly divergent energy levels. The results obtained using a realistic for torsion potential, including computed (near) degeneracies, can be rationalised in terms with no...

Rotational-vibrational states up to 3200 cm-1, beyond the highest-lying stretching fundamental, are computed variationally for vinyl radical (VR), H2Cβ[double bond, length as m-dash]CαH, and following deuterated isotopologues of VR: CH2[double m-dash]CD, CHD[double m-dash]CH, CD2[double m-dash]CD. The height CαH tunneling rocking barrier VR, partially responsible complex nuclear dynamics VR its isotopologues, is determined be 1641 ± 25 cm-1 by focal-point analysis approach. definitive...

The principal purpose of this investigation is the determination tunneling half-lives trans -HCSH → H 2 CS and -HCSeH CSe unimolecular isomerization reactions at temperatures close to 0 K. To aid these determinations, accurate electronic structure computations were performed, with electron correlation treatments as extensive CCSDT(Q) basis sets large aug-cc-pCV5Z, for isomers [H,H,C,S] [H,H,C,Se] on their lowest singlet surfaces appropriate transition states yielding structural data key...

Abstract The rotation-vibration (Coriolis) coupling contribution to variationally computed rovibrational energy levels is investigated, employing triatomic AB $${}_{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> molecules as models. In particular, calculations are performed for H $${}^{16}$$ <mml:msup> <mml:mn>16</mml:mn> </mml:msup> O, across a range of vibrational and rotational...

Exact quantum dynamics calculations are performed for the bound rovibrational states of neon tetramer (Ne4) in its ground electronic state, using pair-wise Lennard-Jones potentials and ScalIT suite parallel codes. The vibrational separate into a low-lying group mostly localized to single potential well higher-energy delocalized lying above isomerization threshold—with such structure serving as testament “intermediate” nature Ne4 system. To accurately efficiently represent both groups states,...

Methods for solving the Schrödinger equation without approximation are in high demand but notoriously computationally expensive. In practical terms, there just three primary factors that currently limit what can be achieved: 1) system size/dimensionality; 2) energy level excitation; and 3) numerical convergence accuracy. Broadly speaking, current methods deliver on any two of these goals, achieving all at once remains an enormous challenge. this paper, we shall demonstrate how to "hit...

The ongoing shift toward clean, sustainable energy is a primary driving force behind hydrogen fuel research. Safe and effective storage of major challenge (particularly for mobile applications) requires detailed understanding the atomic level interactions with its host materials. light mass hydrogen, however, implies that quantum effects are important, so dynamical treatment required to properly account these in computational simulations. As one such example, we describe herein exchange...

H 3 + is a key player in molecular astrophysics, appearing the interstellar medium and atmospheres of gas giants. It also plays an important role star formation, it has been detected supernova remnants. In theoretical chemistry, H3+ long benchmark polyatomic system for high-level electronic-structure computations, as well quantum dynamics studies. this work, exact dynamical calculations are carried out H3+, using ScalIT suite parallel codes, applied to two spectroscopically accurate...

In a recent article [AIP Adv. 11, 045033 (2021)], we carried out exact quantum dynamical calculations and computed ro-vibrational energy levels wave functions for the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math> molecular ion up to dissociation threshold (at J = 46) using recently developed...