Magnetic field induced alignment-orientation conversion: Nonlinear energy shift and predissociation in Te-2 B1(u) state

The paper analyzes magnetic field induced alignment-orientation conversion (AOC) phenomenon caused by simultaneous effect of quadratic terms in Zeeman energy shift and magnetic predissociation (PD), producing asymmetry either in energy splitting omega(MM+/-1)not equal omega-(M-/+1-M) or in relaxation of coherence Gamma(MM+/-1)(not equal Gamma)-(M-/+-M) between coherently excited M, M+/-1 magnetic sublevels. The AOC is registered via the appearance of circular polarization (C) of fluorescence under linearly polarized excitation. The unified perturbation treatment of a molecule in external magnetic field B is presented, accounting for magnetic and intramolecular perturbations via interaction with bonded or continuum states, considering Hund's (c)-case coupling and dividing the intramolecular perturbation operator into homogeneous (Delta Omega=0) and heterogeneous (Delta Omega=+/-1) parts. Explicit expressions up to B-2 terms are given for energy shift and PD rate, adapted to 1(u) state in conditions relevant to the B-3 Sigma(u)(-) complex of Te-2 molecule. Numeric simulation revealed that nonlinear magnetic energy shift and heterogeneous magnetic PD produce dispersion type fluorescence circularity signals C(B) of different sign. Fitting of experimental data on B1(u)(-), upsilon(J)=2(96) state of Te-130(2) molecule allowed to determine the electronic matrix element of paramagnetic Hamiltonian (Omega=0\(H) over cap(pm)\Omega=1)=G(+/-)=2.7, as well as the natural C-upsilon(het) = +/-6 s(-1/2) and the magnetic alpha(upsilon)(het) =-/+ 9 X 10(3) s-1/2 T-1 rate constants of heterogeneous PD, supposing that the B1(u)(-) state PD takes place through O-u(-) state continuum. As a result, magnetic AOC represents a sensitive method to investigate molecular structure and intramolecular interaction between both bonded and continuum states. Additionally, it has been shown that the magnetic PD effect leads to strong amplification of nonzero field level crossing signals caused by B-2 terms in Zeeman energy shift. (C) 1996 American Institute of Physics.