Related papers: Transition from molecular complex to quantum solva…
A theoretical study is reported of the molecular-to-atomic transition in solid hydrogen at high pressure. We use the diffusion quantum Monte Carlo method to calculate the static lattice energies of the competing phases and a…
Monte Carlo methods are used to study the phase transition in ammonium chloride from the orientationally ordered $\delta$ phase to the orientationally disordered $\gamma$ phase. An effective pair potential is used to model the interaction…
We investigate the finite nuclear mass corrections in the helium atom in order to resolve a significant disagreement between the $2^3S - 2^3P$ and $2^3S - 2^1S$ transition isotope shifts. These two transitions lead to discrepant results for…
High resolution spectroscopy of doped molecules in 4He nano-droplets and clusters gives a signature of superfluidity in microscopic system, termed as microscopic superfluidity. Ro-vibrational spectrum of 4HeN-M clusters is studied with the…
We present calculations of rotational absorption spectra of the molecules HCN and DCN in superfluid helium-4, using a combination of the Diffusion Monte Carlo method for ground state properties and an analytic many-body method (Correlated…
The compressibility of solid helium (3He and 4He) in the hcp and fcc phases has been studied by path-integral Monte Carlo. Simulations were carried out in both canonical (NVT) and isothermal-isobaric (NPT) ensembles at temperatures between…
The rotational constant parametrizes the relative spacing between a molecule's rotational energy levels. It depends on the molecule's classical moments of inertia, which, in all studies, are expressed by treating the constituent nuclei as…
Resonant vibrational-excitation cross sections and rate constants for electron scattering by molecular oxygen are presented. Transitions between all 42 vibrational levels of O$_2(\textrm{X}\ ^3\Sigma_g^- $) are considered. Molecular…
The ground and excited state properties of small helium clusters, 4He_N, containing nanoscale (~3-10 Angstroms) planar aromatic molecules have been studied with quantum Monte Carlo methods. Ground state structures and energies are obtained…
We study the hydrodynamics of quantum 4He crystal oscillations in a superfluid liquid with involving the dynamics of atomically rough surfaces. It is shown that, due to enhancement of the kinetic growth coefficient as the temperature…
We study the zero-temperature phase diagram of two-dimensional helium-4 using neural quantum states. Our variational description allows us to address liquid and solid phases using the same functional form as well as exploring possible…
Helium excimers generated by a corona discharge were investigated in the gas and normal liquid phases of helium as a function of temperature and pressure between 3.8 and 5.0 K and 0.2 and 5.6 bar. Intense fluorescence in the visible region…
When the density of a nuclear system is decreased, homogeneous states undergo the so-called Mott transition towards clusterised states, e.g. alpha clustering, both in nuclei and in nuclear matter. Here we investigate such a quantum phase…
We present a new class of quantum phase transitions that refer neither to local order parameter and critical fluctuations nor to continuous symmetry breaking but are assigned by the step-wise change in topology of the multi-particle system…
In this paper we use the important interferences of Macro-Orbital theory of superfluidity clubbed with several factors that can change the rotational constant (B) and vibrational frequency of N2O in 4HeN-N2O clusters with N to account for…
Carbon monoxide is a simple molecule present in many astrophysical environments, and collisional excitation rate coefficients due to the dominant collision partners are necessary to accurately predict spectral line intensities and extract…
Using Path Integral Monte Carlo we calculate exchange frequencies in bulk hcp 4He as atoms undergo ring exchange. We fit the frequencies to a lattice model and examine whether such atoms could become a supersolid, that is have a…
Cold molecules are important for many applications, from fundamental precision measurements, quantum information processing, quantum-controlled chemistry, to understanding the cold interstellar medium. Molecular ions are known to be cooled…
Experimental observation of superfluidity in a microscopic cluster, $M:(^4He)_x$, of a molecule ($M$) and $x$ number of $^4He$ atoms (with $x$ ranging from 1 to many) is qualitatively analyzed. It concludes that: (i) each $^4He$ atom in the…
We use quantum-logic spectroscopy (QLS) and interrogate rotational transitions of a single CaH+ ion with a highly coherent frequency comb, achieving a fractional statistical uncertainty for a transition line center of 4 x 10^-13. We also…