Spectroscopy of superheavy hydrogen isotopes in stopped-pion absorption by nuclei

The structure of levels of superheavy hydrogen isotopes {sup 4-6}H is analyzed on the basis of a record statistics of experimental data on the absorption of negatively charged pions by light nuclei. Qualitatively new experimental data are obtained for the spectroscopy of the superheavy hydrogen isotopes {sup 5}H and {sup 6}H. Peaks due to four resonance states of {sup 5}H are observed in the missing-mass spectra for the reaction channels {sup 9}Be({pi}{sup -}, pt)X and {sup 9}Be({pi}{sup -}, dd)X. A structure that is associated with four resonance states of {sup 6}H is observed in the missing-mass spectra for the reaction channels {sup 9}Be({pi}{sup -}, pd)X and {sup 11}B({pi}{sup -}, p{sup 4}He)X. On the basis of the results presented for ground-state parameters, it can be concluded that the binding energy of superheavy hydrogen isotopes decreases as the number of neutrons increases. Excited levels of the isotopes {sup 5}H and {sup 6}H are observed for the first time. On the energy scale, all of these states lie above the threshold for decay to free nucleons.