The NaLi electronic ground state studied by laser induced fluorescence and Fourier transform spectroscopy

Quantum Dynamics Studies of the Li + Na2 (V = 0, j = 0) → Na + NaLi Reaction on a New Neural Network Potential Energy Surface

The ultracold reaction offers a unique opportunity to elucidate the intricate microscopic mechanism of chemical reactions, and the Na2Li system serves as a pivotal reaction system in the investigation of ultracold reactions. In this work, a high-precision potential energy surface (PES) of the Na2Li system is constructed based on high-level ab initio energy points and the neural network (NN) method, and a proper asymptotic functional form is adopted for the long-range interaction, which is suitable for the study of cold or ultracold collisions. Based on the new NN PES, the dynamics of the Li + Na2 (v = 0, j = 0) → Na + NaLi reaction are studied in the collision energy range of 10-7 to 80 cm-1. In the high collision energy range of 8 to 80 cm-1, the dynamics of the reaction is studied using the time-dependent wave packet method and the statistical quantum mechanical (SQM) method. Comparing the results of the two methods, it is found that the SQM method provides a rough description of the product ro-vibrational state distribution but overestimates the integral cross-section values. With the decrease of collision energy, the reaction differential cross section gradually changes from forward-backward symmetric scattering to predominant forward scattering. In the low collision energy range from 10-7 to 8 cm-1, the SQM method is used to study the reaction dynamics, and the rate constant in the Wigner threshold region is estimated to be 2.87 × 10-10 cm3/s.

Achieving vibrational energies of diatomic systems with high quality by machine learning improved DFT method

When using ab initio methods to obtain high-quality quantum behavior of molecules, it often involves a lot of trial-and-error work in algorithm design and parameter selection, which requires enormous time and computational resource costs. In the study of vibrational energies of diatomic molecules, we found that starting from a low-precision DFT model and then correcting the errors using the high-dimensional function modeling capabilities of machine learning, one can considerably reduce the computational burden and improve the prediction accuracy. Data-driven machine learning is able to capture subtle physical information that is missing from DFT approaches. The results of 12C16O, 24MgO and Na35Cl show that, compared with CCSD(T)/cc-pV5Z calculation, this work improves the prediction accuracy by more than one order of magnitude, and reduces the computation cost by more than one order of magnitude.

Spectroscopic study of the E(4)1sigma+ state in NaLi

Polarization labelling spectroscopy is applied to study the excited E1sigma+ state of NaLi in the energy range 26,500-28,000 cm(-1) above the bottom of the ground state. The potential curve of the E state is constructed using the Inverted Perturbation Approach method. The values of Te, omega(e) and Re are found to be 26,474.82(4), 180.3(2) cm(-1) and 3.343(1) A, respectively.

The Ground State X1Sigma+ of NaK Revisited

Laser-induced fluorescence (LIF) optical spectra of the D1Pi-X1Sigma+ system of the NaK molecule have been reinvestigated. In this new analysis, quantum numbers have been assigned to 3000 selected fluorescence lines for a wide range of vibrational and rotational levels (J </= 149, v' </= 23, v" </= 47). A new set of constants of the X1Sigma state (Dunham-type coefficients) and term values of the D1Pi state have been determined by a weighted least-squares fit of the LIF optical lines of the D-X system, some lines of the C-X system, and microwave spectral data reported recently. Constants for X1Sigma (in cm-1) are as follows: omegae = 123.993, omegaexe = 0.3045, Be = 0.095229, and alphae = 4.48 x 10(-4). The equilibrium internuclear distance is re = 3.49903 Å, very little changed from the microwave value. Copyright 1998 Academic Press.