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1. Two-photon spectroscopy of the NaLi triplet ground state

   https://doi.org/10.1039/C7CP08481A  

   Rvachov, Timur M.; Son, Hyungmok; Park, Juliana J.; Ebadi, Sepehr; Zwierlein, Martin W.; Ketterle, Wolfgang; Jamison, Alan O. (January 2018, Physical Chemistry Chemical Physics)

   We employ two-photon spectroscopy to study the vibrational states of the triplet ground state potential (a 3 Σ + ) of the 23 Na 6 Li molecule. Pairs of Na and Li atoms in an ultracold mixture are photoassociated into an excited triplet molecular state, which in turn is coupled to vibrational states of the triplet ground potential. Vibrational state binding energies, line strengths, and potential fitting parameters for the triplet ground a 3 Σ + potential are reported. We also observe rotational splitting in the lowest vibrational state. 

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2. Efficient pathway to NaCs ground state molecules

   https://doi.org/10.1088/1367-2630/acd411  

   Warner, Claire; Bigagli, Niccolò; Lam, Aden Z; Yuan, Weijun; Zhang, Siwei; Stevenson, Ian; Will, Sebastian (May 2023, New Journal of Physics)

   Abstract We present a study of two-photon pathways for the transfer of NaCs molecules to their rovibrational ground state. Starting from NaCs Feshbach molecules, we perform bound-bound excited state spectroscopy in the wavelength range from 900 nm to 940 nm, covering more than 30 vibrational states of the c 3 Σ + , b 3 Π , and B 1 Π electronic states. Analyzing the rotational substructure, we identify the highly mixed c 3 Σ 1 +   | v = 22 ⟩ ∼ b 3 Π 1   | v = 54 ⟩ state as an efficient bridge for stimulated Raman adiabatic passage. We demonstrate transfer into the NaCs ground state with an efficiency of up to 88(4)%. Highly efficient transfer is critical for the realization of many-body quantum phases of strongly dipolar NaCs molecules and high fidelity detection of single molecules, for example, in spin physics experiments in optical lattices and quantum information experiments in optical tweezer arrays. 

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3. Dynamic signatures of electronically nonadiabatic coupling in sodium hydride: a rigorous test for the symmetric quasi-classical model applied to realistic, ab initio electronic states in the adiabatic representation

   https://doi.org/10.1039/d1cp04090a  

   Talbot, Justin J.; Head-Gordon, Martin; Miller, William H.; Cotton, Stephen J. (February 2022, Physical Chemistry Chemical Physics)

   Sodium hydride (NaH) in the gas phase presents a seemingly simple electronic structure making it a potentially tractable system for the detailed investigation of nonadiabatic molecular dynamics from both computational and experimental standpoints. The single vibrational degree of freedom, as well as the strong nonadiabatic coupling that arises from the excited electronic states taking on considerable ionic character, provides a realistic chemical system to test the accuracy of quasi-classical methods to model population dynamics where the results are directly comparable against quantum mechanical benchmarks. Using a simulated pump–probe type experiment, this work presents computational predictions of population transfer through the avoided crossings of NaH via symmetric quasi-classical Meyer–Miller (SQC/MM), Ehrenfest, and exact quantum dynamics on realistic, ab initio potential energy surfaces. The main driving force for population transfer arises from the ground vibrational level of the D 1 Σ + adiabatic state that is embedded in the manifold of near-dissociation C 1 Σ + vibrational states. When coupled through a sharply localized first-order derivative coupling most of the population transfers between t = 15 and t = 30 fs depending on the initially excited vibronic wavepacket. While quantum mechanical effects are expected due to the reduced mass of NaH, predictions of the population dynamics from both the SQC/MM and Ehrenfest models perform remarkably well against the quantum dynamics benchmark. Additionally, an analysis of the vibronic structure in the nonadiabatically coupled regime is presented using a variational eigensolver methodology. 

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4. Proton relays in anomalous carbocations dictate spectroscopy, stability, and mechanisms: case studies on C ₂ H ₅ ⁺ and C ₃ H ₃ ⁺

   https://doi.org/10.1039/C7CP05577C  

   Sager, LeeAnn M.; Iyengar, Srinivasan S. (January 2017, Phys. Chem. Chem. Phys.)

   We present a detailed analysis of the anomalous carbocations: C 2 H 5 + and C 3 H 3 + . This work involves (a) probing electronic structural properties, (b) ab initio dynamics simulations over a range of internal energies, (c) analysis of reduced dimensional potential surfaces directed along selected conformational transition pathways, (d) dynamically averaged vibrational spectra computed from ab initio dynamics trajectories, and (e) two-dimensional time–frequency analysis to probe conformational dynamics. Key findings are as follows: (i) as noted in our previous study on C 2 H 3 + , it appears that these non-classical carbocations are stabilized by delocalized nuclear frameworks and “proton shuttles”. We analyze this nuclear delocalization and find critical parallels between conformational changes in C 2 H 3 + , C 2 H 5 + , and C 3 H 3 + . (ii) The vibrational signatures of C 2 H 5 + are dominated by the “bridge-proton” conformation, but also show critical contributions from the “classical” configuration, which is a transition state at almost all levels of theory. This result is further substantiated through two-dimensional time–frequency analysis and is at odds with earlier explanations of the experimental spectra, where frequencies close to the classical region were thought to arise from an impurity. While this is still possible, our results here indicate an additional (perhaps more likely) explanation that involves the “classical” isomer. (iii) Finally, in the case of C 3 H 3 + our explanation of the experimental result includes the presence of multiple, namely, “cyclic”, “straight”, and propargyl, configurations. Proton shuttles and nuclear delocalization, reminiscent of those seen in the case of C 2 H 3 + , were seen all through and have a critical role in all our observations. 

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5. ALMA-IMF: XIX. C ¹⁸ O ( J = 2–1): Measurements of turbulence in 15 massive protoclusters

   https://doi.org/10.1051/0004-6361/202553830  

   Koley, A; Stutz, A M; Louvet, F; Motte, F; Ginsburg, A; Galván-Madrid, R; Álvarez-Gutiérrez, R H; Sanhueza, P; Baug, T; Sandoval-Garrido, N; et al (October 2025, Astronomy & Astrophysics)

   ALMA-IMF is a Large Program of the Atacama Large Millimeter/submillimeter Array (ALMA) that aims to determine the origin of the core mass function (CMF) of 15 massive Galactic protoclusters (~1.0–25.0 × 10³M_⊙within ~2.5 × 2.5 pc²) located toward the Galactic plane. In addition, the objective of the program is to obtain a thorough understanding of their physical and kinematic properties. Here we study the turbulence in these protoclusters with the C¹⁸O (2–1) emission line using the sonic Mach number analysis (M_s) and the size-linewidth relation. The probability distribution functions (PDFs) forM_sshow a similar pattern, exhibiting no clear trend associated with evolutionary stage, peaking in the range between 4 and 7, and then extending to ~25. Such values ofM_sindicate that the turbulence in the density regime traced by the C¹⁸O line inside the protoclusters is supersonic in nature. In addition, we compared the non-thermal velocity dispersions (σ_nth,C¹⁸O) obtained from the C¹⁸O (2–1) line with the non-thermal line widths (σ_{nth, DCN}) of the cores obtained from the DCN (3–2) line. We observed that, on average, the non-thermal linewidth in cores is half that of the gas surrounding them. This suggests that turbulence diminishes at smaller scales or dissipates at the periphery of the cores. Furthermore, we examined the size-linewidth relation for the structures we extracted from the position-position-velocity C¹⁸O (2–1) line emission cube with the dendrogram algorithm. The power-law index (p) obtained from the size-linewidth relation is between 0.41 and 0.64, steeper than the Kolmogorov law of turbulence, as expected for compressible media. In conclusion, this work is one of the first to carry out a statistical study of turbulence for embedded massive protoclusters. 

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