Infrared spectra and tunneling dynamics of the N2–D2O and OC–D2O complexes in the v2 bend region of D2O

Understanding the high-resolution spectral signature of the N2-H2O van der Waals complex in the 2OH stretch region

We present the observation of the N2-H2O van der Waals complex in the 2OH stretch overtone region. The high-resolution jet cooled spectra were measured using a sensitive continuous wave cavity ringdown spectrometer. Several bands were observed and vibrationally assigned in terms of ν1, ν2, and ν3, the vibrational quantum numbers of the isolated H2O molecule, as (ν1'ν2'ν3')←(ν1″ν2″ν3″)=(200)←(000) and (101) ← (000). A combination band involving the excitation of the in-plane bending motion of N2 and the (101) vibration of water is also reported. The spectra were analyzed using a set of four asymmetric top rotors, each associated with a nuclear spin isomer. Several local perturbations of the (101) vibrational state were observed. These perturbations were assigned to the presence of the nearby (200) vibrational state and to the combination of (200) with intermolecular modes.

A Hydrophilic Mixed Lanthanide Metal-Organic Framework Monitoring H2O in D2O

Lanthanide metal-organic framework (Ln-MOF) luminescent sensors monitoring the H₂O content in D₂O are still rare. We designed and built a hydrophilic mixed Ln-MOF (Eu_0.4Tb_0.6-MOF) monitoring the H₂O content in D₂O. By designing a ligand and controlling the synthesis method, we achieved a balance between the structural stability and sensing capacity. When the H₂O content ranges from 0 to 100%, the photoluminescence color of Eu_0.4Tb_0.6-MOF can change from yellow to green, which can be observed by the naked eye. The mechanism is that the photoluminescence intensity of Eu³⁺ decreases faster than that of Tb³⁺ when the H₂O content increases. The sensing mechanism was studied further by transient fluorescence spectrometry.

Noncovalently bound molecular complexes beyond diatom–diatom systems: full-dimensional, fully coupled quantum calculations of rovibrational states

The methodological advances made in recent years have significantly extended the range and dimensionality of noncovalently bound molecular complexes for which full-dimensional quantum calculations of their rovibrational states are feasible.

Spectroscopic study of the tunneling dynamics in N2-water observed in the O-D stretch region

The O-D stretch rovibrational spectra of N₂-D₂O and N₂-DOH were measured and analyzed. A combination band involving the in-plane N₂ bending vibration was also observed. These bands were recorded using a pulsed-slit supersonic jet expansion and a mid-infrared tunable optical parametric oscillator. The spectra were analyzed by considering the feasible tunneling motions, and transitions were fitted to independent asymmetric rotors for each tunneling state. The rotational constants of the four tunneling components of N₂-D₂O were retrieved for the excited vibrational states. A two order of magnitude increase in the tunneling splittings is observed for the asymmetric O-D stretch (ν₃ in D₂O) excitation compared to the symmetric stretch (ν₁ in D₂O) and to the ground vibrational state. This last finding indicates that the ν₃ vibrational state is likely perturbed by a combination state that includes ν₁. Finally, the observation of a local perturbation in the ν₃ vibrational band, affecting the positions of few rovibrational levels, provides an experimental lower limit of the dissociation energy of the complex, D₀ > 120 cm^-1.

Explicitly correlated ab initio potential energy surface and predicted rovibrational spectra for H2O-N2 and D2O-N2 complexes

An ab initio intermolecular potential energy surface (PES) for the van der Waals complex of H₂O-N₂ that explicitly incorporates the intramolecular Q₂ bending normal mode of the H₂O monomer is presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory [CCSD(T)-F12] with an augmented correlation-consistent triple zeta basis set and an additional bond function. Analytic five-dimensional intermolecular PESs for ν₂(H₂O) = 0 and 1 are obtained by fitting to the multi-dimensional Morse/long-range potential function form. These fits to 40 890 points have the root-mean-square (rms) discrepancy of 0.88 cm^-1 for interaction energies less than 2000.0 cm^-1. The resulting vibrationally averaged PESs provide good representations of the experimental microwave and infrared data: for microwave transitions of H₂O-N₂, the rms discrepancy is only 0.0003 cm^-1, and for infrared transitions of the A₁ symmetry of the H₂O(ν₂ = 1 ← 0)-N₂, the rms discrepancy is 0.001 cm^-1. The calculated infrared band origin shifts associated with the ν₂ bending vibration of water are 2.210 cm^-1 and 1.323 cm^-1 for H₂O-N₂ and D₂O-N₂, respectively, in good agreement with the experimental values of 2.254 cm^-1 and 1.266 cm^-1. The benchmark tests and comparisons of the predicted spectral properties are carried out between CCSD(T)-F12a and CCSD(T)-F12b approaches.

An accurate full-dimensional permutationally invariant potential energy surface for the interaction between H2O and CO

The first full-dimensional accurate potential energy surface was developed for the CO + H₂O system based onca.102 000 points calculated at the CCSD(T)-F12a/AVTZ level using a permutation invariant polynomial-neural network (PIP-NN) method.

The water–carbon monoxide dimer: new infrared spectra, ab initio rovibrational energy level calculations, and an interesting in-termolecular mode

Bound state rovibrational energy level calculations using a high-level intermolecular potential surface are reported for H₂O–CO and D₂O–CO.

Micro-solvation of CO in water: infrared spectra and structural calculations for (D2O)2–CO and (D2O)3–CO

The weakly-bound molecular clusters (D₂O)₂–CO and (D₂O)₃–CO are observed in the C–O stretch fundamental region (≈2150 cm⁻¹), and their rotationally-resolved infrared spectra yield precise rotational parameters.

The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.