Ortho-para transition in molecular hydrogen

The radiative ortho-para transition in the molecular hydrogen is studied. This highly forbidden transition is very sensitive to relativistic and subtle nonadiabatic effects. Our result for the transition rate in the ground vibrational level \Gamma(J=1\to J=0) = 6.20(62)\cdot 10^{-14} \iyr is significantly lower in comparison to all the previous approximate calculations. Experimental detection of such a weak line by observation of, for example, the cold interstellar molecular hydrogen is at present unlikely.Comment: 4 pages, submitted to Phys. Rev.

Nonadiabatic corrections to rovibrational levels of H2_2

The leading nonadiabatic corrections to rovibrational levels of a diatomic molecule are expressed in terms of three functions of internuclear distance: corrections to the adiabatic potential, the effective nuclear mass, and the effective moment of inertia. The resulting radial Schr\"odinger equation for nuclear motion is solved numerically yielding accurate nonadiabatic energies for all rovibrational levels of H$_2$ molecule in excellent agreement with previous calculations by Wolniewicz.Comment: 14 page

Nonadiabatic corrections to the wave function and energy

Nonadiabatic corrections in molecules composed of a few atoms are considered. It is demonstrated that a systematic perturbative expansion around the adiabatic solution is possible, with the expansion parameter being the electron-nucleus mass ratio to the power 3/4. Closed form formulae for the leading corrections to the wave function and to the energy are derived. Their applicability is demonstrated by a comparison of numerical results for the hydrogen molecule with the former nonadiabatic calculations and the experimental values. Good agreement with the recent experiment is achieved for the ground state dissociation energy of both H$_2$ and D$_2$.Comment: 8 pages, to be published in J. Chem. Phy

APPLICATION OF EXPLICITLY CORRELATED GAUSSIANFUNCTIONS TO LARGE SCALE CALCULATIONS ONSMALL ATOMS AND MOLECULES

Exponentially Correlated Gaussian wave functions are applied to variational calculations of thetotal electronic energy of several a few-electron atomic and molecular systems. It is shown thatthis powerful approach enables to obtain extremely accurate results not only for two-electronsystems but also for three- and four-electron atoms and molecules.Pozna