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Electro-production of pions and kaons at the kinematics of quasi-elastic knockout (which is well known in the physics of atomic nucleus and corresponds to the t-pole diagram) is proposed for obtaining their momentum distribution (MD) in various channels of virtual decay N → B +π, B = N , ∆, N * , N * * , and N → Y +K, Y = Λ, Σ. It is a powerful tool for investigation of a quark microscopic picture of the meson cloud in the nucleon. A model of scalar qq ( 3 P 0 ) fluctuation in the non-trivial QCD vacuum is used to calculate pion and kaon momentum distributions (MD) in these channels. 1 In the constituent quark model the pion charge radius includes contributions both quarks and the ρ-meson pole (the vector meson dominance model): [< r 2 π > ch ] 1/2 = [3b 2 π /4 + 6/m 2 ρ ] 1/2 ≃ 0.68 fm.

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Collisions of metastable antiprotonic helium with medium atoms induce transitions between hyperfine structure sublevels as well as shift and broadening of the microwave M1 spectral lines. We consider these effects in the framework of a simple model with scalar and tensor interactions between (pHe + ) nL and He atoms. Smatrix is obtained by solving coupled-channels equations involving 4 HFS sublevels (F = L ± 1/2, J = F ± 1/2) of the nL level and relative angular momenta up to l = 5 at the kinetic energy E 10 K. The calculated spin-flip cross sections are less than elastic ones by 4 orders of value. At the density N = 3 × 10 20 cm −3 and T = 6 K we obtain the relaxation times τ (F J → F ′ J ′ ) 160 ns, the frequency shifts of M1 spectral lines ∆ν 66 KHz for the favored transitions (∆F = ±1, ∆J = ±1) and frequency broadening of the M1 spectral lines γ/2 5.8 MHz. The results are compatible with the recent experimental data obtained by a laser-microwave-laser resonance method.Key words: antiproton, antiprotonic helium, hyperfine structure, collisional relaxation, collisional shift and broadening 34.60.+z, 32.70.Jz The discovery of antiproton longevity in helium and investigations of antiprotonic helium (pHe + ) metastable states by the method of laser resonance spectroscopy have opened a new layer of very interesting physics (see [1] and the references therein). One of the actual problems in the topics is an influence of ambient atoms on the antiprotonic states. In particular, the density shifts and broadenings of E1 spectral lines (nL → n ′ L ′ = L ± 1) were observed for laserinduced transitions. The model theoretical analysis [2] shows that qualitative