# Interaction of tunneling systems

Our work is dedicated to the investigation of the environmental effect on quantum tunneling of atoms in glasses when coupled with their nuclear magnetic moments and on positive charge transfer between base pairs of DNA in polar solvent We considered the effect of internal nuclear quadrupole interaction on quantum tunneling in complex multiatomic two-level systems and found two distinct regimes of strong and weak interactions. These regimes depend on the relationship between characteristic energy of the nuclear quadrupole interaction b* and bare tunneling coupling strength Delta0. When Delta0 > b* the internal interaction is negligible and tunneling remains coherent as determined by Delta 0. When Delta0 < b*, coherent tunneling breaks down and effective tunneling amplitude decreases by an exponentially small overlap factor eta* ≪ 1 between internal ground states of left and right wells of a tunneling system. This consequently affects the thermal and kinetic properties of tunneling systems at low temperatures T < b*. By the application of this theory, we can interpret the anomalous behavior of the resonant dielectric susceptibility in amorphous solids at low temperatures T < 5 mK, where nuclear quadrupole interaction breaks down coherent tunneling. We suggest conducting experiments with external magnetic fields to test our predictions and to clarify the internal structure of tunneling systems We also studied the tunneling of positive charge in DNA, which is another example of tunneling under conditions of strong interaction with the environment. The tight-binding Hamiltonian containing a quantum electron exchange integral and supplied by a classical linear interaction of the charge in DNA with water solvent polarization is taken to describe the experimental dynamics of the charge transfer reactions. Equilibrium constants of positive charge transfer between single, double guanine-cytosine (GC) and triple GC3 base pairs through the bridging adenine-thymine base pair were reproduced together with the corresponding differences in free energies. The effect of localization by the solvent polarization is shown to be much stronger than that of the quantum delocalization of the charge, which creates an asymmetric charge distribution in the ground state of the symmetric DNA base-pair sequences