Search

Highly excited states of 6He are sought in the reactions involved in the absorption of stopped pions by 10,11B nuclei. Several levels in 6He are observed for the first time. A state with Ex ≈ 9.3(2) MeV and Γ ≈ 1.0(4) MeV is seen to form in two reactions: 10B(π−, pt)X and 11B(π−, dt)X. Two states are seen to form in the 10B(π−, pt)X reaction channel at energies above the threshold of 6He decay into two tritons (Ex ≥ 12.3 MeV): one state with Ex = 22(1) MeV, Γ = 2.7(1.4) MeV and the other with Ex = 27.0(8) MeV, Γ = 2.5(1.1) MeV.

Search for isobar-analog states (IAS) of superheavy hydrogen isotopes 5-7H was performed among the high-excited states of helium isotopes 5-7He. The excited spectra were measured in stopped pion absorption by light nuclei. The experiment was performed at low energy pion channel of LANL with two-arm multilayer semiconductor spectrometer. Excited states of 5-7He were observed in three-body reaction channels on 10,11B nuclei. Several excited levels were observed for the first time. 6He excited state with Ex = 27.0(8) MeV observed in 10B(π-,pt)X channel is an IAS candidate for 6H with Er ~ 5.5 MeV. 7He excited state with Ex = 24.8(4) MeV observed in 10B(π-,pd)X, nB(π-,pt)X and nB(π-,dd)X channels is an IAS candidate for 7H with Er ~ 3 MeV.

A channel formed by self-focusing of 30-ps pump pulses of wavelength 1.06 μm and energy of up to 40 mJ in high-pressure hydrogen (with a pressure of up to 120 atm) was probed by second-harmonic pulses delayed in time with respect to the pump pulses. This revealed scattering of efficiency which increased from zero to almost total scattering with increasing delay time. The effect is interpreted as scattering by optical inhomogeneities formed by an acoustic perturbation excited under conditions of a nonuniform temperature distribution along the self-focusing channel.