Quenching of metastable hydrogen atoms by low energy collisions with hydrogen molecules: comparison of experiments with theory

Coherence effects in the polarization of Lyman-α fluorescence following photodissociation of H2 and D2

“…[33][34][35][36][37][38][39][40][41][42][43] This 2s -2p mixing, due to the H 2 quadrupole-H dipole interaction, is the principal mechanism of the collisional quenching of the metastable atoms. However, a radiationless quenching of the H(2s) atoms has also been reported, 33,35,42,43 detected by using an electrical quenching of the metastable atoms.…”

“…Taking into account the influence of the rotation of the hydrogen molecule on the cross section more accurately, the quenching cross sections are expected to show no variation with v at 137 K and a v Ϫ1/3 -dependence at 300 K for the velocity range between 3 and 8 km s Ϫ1 . 41 Under these conditions, the disaligning parameter f 137 for 137 K can be written as…”

Collisions between Metastable Hydrogen Atoms at Thermal Energies

“…We find also that double excitation transfer into two excited H͑2p͒ atoms is still more probable with the large cross section of 9 3 10 212 cm 2 at E 4.1 meV varying as E 21͞2 at higher energies. The detection of the resulting Lyman alpha photons would provide a diagnostic test of our predictions.Several experiments involving interactions of metastable hydrogen atoms with various targets have been performed [1][2][3][4][5][6][7][8]. The theoretical simplicity of atomic hydrogen makes it an ideal system for studying fundamental physics.…”

Collisions at thermal energy between metastable hydrogen atoms and hydrogen molecules: total and differential cross sections

“…The first one emerges from an atomic point of view: H*(2s) is quenched by the multipolar (in fact quadrupolar) electrical field of the H2 molecule which mixes the 2s and 2p states of H* and this process represents a simple absorption for the elastic scattering [4,8]. Assuming a straight line trajectory, the calculation leads to an integral radiative cross section ~Ly= the velocity dependence of which fits rather well the experimental data but the absolute values of which are rather dubious because of the use of a cut-off impact parameter.…”

“…Nevertheless only integral total cross sections [1-4], quenching total cross sections [5] and reaction rates for the associative ionization [6] have been measured so far. Theoretical studies of H* and H f are of two different types (with no overlapping up to now): (i) molecular calculations [7]; (ii) treatment of the collisional quenching [4,8]. The purpose of the present work is to extend integral cross section measurements towards lower energies (down to 0.06 eV), to measure total differential cross sections, as well as to propose an interpretation in term of long range potentials.…”