The total scattering cross sections for H2+H2, D2+D2, and HD+HD for relative collision energies below 10 meV

Abstract

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.

Ultracold collisions between two light indistinguishable diatomic molecules: Elastic and rotational energy transfer in HD+HD

“…In Fig. 2 we show results of this work computed with the modified BMKP PES [29] together with the corresponding data (experiment/theory) from relatively old papers [20]. As can be seen all these cross sections are in a satisfcatory agreement with each other.…”

“…HD(j1)+HD(j2) b). para-H2(j1)+para-H2(j2) HD(j1)+HD(j2) → HD(j ′ 1 ) + HD(j ′ 2 ) H2(j1) + H2(j2) → H2(j ′ 1 ) + H2(j ′ 2 ) [29] together with the experimental and theoretical data from work [20].…”

“…Surprisingly, such a fundamental and attractive quantum four-atomic system has not received substantial attention in previous experimental and theoretical investigations. Several molecular-beam studies of HD+HD involve the measurement of a few rotational probabilities [19], integral cross sections for unresolved internal [20], and rotational energy transfer rates [21,22]. Nevertheless, there are only a few calculations dealing with the rotational excitation in the HD+HD collision, e. g., an early modified-wave-number calculation by Takayanagi [23], semiclassical calculations by Gelb and Alper [24], and Cacciatore and Billing [25].…”

A comparative study of the low energy HD+o-/p-H2 rotational excitation/de-excitation collisions and elastic scattering

“…Although, this system bears some similarity with H 2 +H 2 , the identical system symmetry is broken here and hence many aspects of the theoretical formulation can be tested in the system under different symmetry conditions. 4,[16][17][18][19][20][21][22] The PESs of H 2 +H 2 and HD-H 2 are basically the same six-dimensional functions. The fact follows from a general theoretical point of view and the Born-Oppenheimer model.…”

“…Many theoretical and experimental methods have been developed and used for the study of these processes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Additionally, there has been great interest in the study of HD+H 2 scattering. Although, this system bears some similarity with H 2 +H 2 , the identical system symmetry is broken here and hence many aspects of the theoretical formulation can be tested in the system under different symmetry conditions.…”