Relative total scattering cross sections for normal H2+normal H2, para-H2+para-H2, normal D2+normal D2, ortho-D2+ortho-D2, and HD+HD were measured at energy below 10 meV by colliding particles from two inclined nozzle beams. Cross sections for the H2+H2 pairs were measured over a relative velocity range of 200–1450 m/s; the normal H2+normal H2 results suggest a l=3 orbiting resonance near 375 m/s while the para-H2+para-H2 results have a l=4 orbiting resonance near 585 m/s. This latter resonance has a peak energy of 1.79 meV and a FWHM of 1.05 meV. The D2+D2 cross sections were measured over the velocity range of 190 to 1000 m/s and a minimum between the l=4 and l=5 orbiting resonances was observed. Some preliminary measurements on HD+HD over the range of 250–1250 m/s indicate a possible l=4 orbiting resonance near 300 m/s. The experimental work compares favorably to cross sections calculated from a theoretical potential.

Experimental total cross section measurements for the He+Ne atom pairs are presented over the relative velocity range of 88 to 1200 m/sec. One orbiting resonance is observed at 160 m/sec. The data around 100 m/sec are consistent with the existence of another resonance at 88 m/sec. A comparison of experimental results to calculated cross sections gives the best fit for the HFD potential. This fit suggest that the lowest velocity resonance is from an l=3 partial wave, while the higher velocity resonance is from an l=4 partial wave.

Total scattering cross-section measurements for 'He+ 'He and 'He+ 'He are presented for velocities between 60 and 900 m/sec and 105 to 1000 m/sec, respectively. For 'He+ He, a Ramsauer-Townsend effect is resolved and s and d phase shifts are obtained. The behavior of the s phase shift suggests that this system is not bound. For 'He+ 'He a virtual state at 135 m/sec is resolved and some p phase shifts are obtained. A fit to the data for both pairs indicates that mass-polarization effects are negligible.

Molecular beam apparatus with supersonic O2 beam (700-3000 m/sec) for reactive scattering experiments with metal atoms Rev. Sci. Instrum. 47, 667 (1976); 10.1063/1.1134719 D2-D2 total scattering cross sections in the velocity range 950-2250 m/sec

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