2004/11/18 by G. Ya. Korenman, Korenman, G. Ya., S. N. Yudin +1
Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic and Molecular Physics #FOS: Physical sciences #Nuclear Theory (nucl-th) #Quantum, superfluid, helium dynamics #nucl-th
paper · pdf · doi:10.48550/arxiv.nucl-th/0411077
12 pages,6 figures
arxiv created 2004/11/18 · openalex publication_date 2004/11/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Collisions of metastable antiprotonic helium with atoms of medium induce transitions between hyperfine structure sublevels as well as shifts and broadenings of the microwave M1 spectral lines. We consider these phenomena in the framework of a model with scalar and tensor interactions between antiprotonic and ordinary helium atoms. S-matrix 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<25 K. The calculated spin-flip cross sections are less than elastic ones by four orders of value in the case ΔJ=± 1, and by seven orders of value in the case ΔF=± 1, ΔJ=0 or ΔJ=± 2. The considered cross sections reveal a resonance behaviour at very low energy (E about 1 - 4 K depending on the model parameters). At the density N=3× 1020 cm-3 and T=6 K we obtain the relaxation time =160 ns, the frequency shift Δν = 80 kHz and the frequency broadening γ\lesssim 5.9 MHz for M1 spectral lines of the favored transitions (ΔF=± 1, ΔJ=± 1). The results are compatible with the recent experimental data obtained by a laser-microwave-laser resonance method. With the temperature rising up to 25 K the rate of relaxation λ=1/τas well as shift and broadening of the M1 microwave lines are lowered by a factor 1.5 - 2 reflecting the displacement of a mean kinetic energy from the region of resonance scattering.