V Kempter

ELECTRONIC EXCITATION OF K ATOMS IN COLLISIONS WITH DIATOMIC MOLECULES: THRESHOLDS AND ENERGY DEPENDENCE FROM 1-5 eV

Abstract A velocity selected atomic potassium beam produced by sputtering has been utilized to study collisional excitation of K atoms by diatomic molecules. K*(42P) was detected by its radiative decay. For N2. NO and O2 the excitation thresholds coincide with the endoergicity of the 42P a 42P transition, 1.6 eV (c.m.s.) whereas for CO the threshold occurs at 2.1 eV. The cross sections rise about linearly with velocity above threshold and are of the order of 2A2 at 4 eV.

Quenching cross sections for alkali-inert gas collisions

The cross sections for quenching the lowestn2P states of the alkali atoms Li, Na, K., and Rb by the inert gases He, Ne, Ar, Kr, and Xe are presented for 5 eV≦Ec.m.≦ 100 eV. These cross sections are derived from the corresponding cross sections for collisional excitation by applying the principle of microreversibility. Upper estimates for the quenching cross sections at thermal energies are given; in all studied cases the quenching cross sections are <8·10−3Å2. These new upper limits are in most cases much lower than those obtained from other methods previously.

EXCITATION CROSS SECTIONS FOR COLLISIONS OF ALKALI ATOMS WITH MOLECULES: THRESHOLDS AND ENERGY DEPENDENCE FROM 1 TO 10 eV.

Abstract Sputtered Na and K beams have been used to study collisional excitation of alkali atoms by molecules. Na * (3 2 P)- and K * (4 2 P) was detected by its radiative decay. There are some indications that excitation of other states may play an important role at higher energies.

Excitation processes in low-energy collisions between ground state helium atoms

Apparent threshold energies have been measured for excitation of the He states 21P, 31D, 33P, 33D, 41S, and 43S in collisions between ground state He atoms. The energy dependence of the cross sections for emission of the He lines 21P to 11S, 33P to 23S, 31D to 21P, 33D to 23P, 41S to 21P, and 43S to 23P has been measured from the respective thresholds up to about 600 eV collision energy. Estimates are given for the absolute values of the cross sections in this range. The emission from states He(3D) shows structure which is due to phase-interface effects.

Scattering of Potassium from Halogen Compounds at Hyperthermal Energies

A potassium atomic beam with energies from 0.5 to 12 eV has been produced by sputtering. The differential elastic cross sections for scattering from C6H12, CCl4, SiCl4, SnCl4, Cl2, and Br2 have been measured. The known behavior of these systems at thermal energies is reproduced to some extent, but there are distinct differences at higher energies for SnCl4, Cl2, and Br2. These may possibly be explained by the onset of nonadiabatic transitions between almost‐crossing energy surfaces.

Study of the optical emission in collisions between rare-gas atoms: spectra of the emitted radiation

The optical spectra between 3300 and 8800 AA were studied at collision energies below about 700 eV for He+He, Ne, Ar, Ne+Ne, Ar and Ar+Ar. Relative cross sections for population of the lowest excited states were derived. For He+He the strong excited He(1snl) states with n>or=3 are He(31P) and He(33D). The strongest emission in all cases involving Ne and Ar atoms was due to the decay of the lowest np5(n+1)p levels of Ne and Ar. Considerable excitation of higher levels was observed for He+Ne, He+Ar and Ar+Ar. For the asymmetrical combinations, excitation of the heavier collision partner is always much stronger than that of the lighter particle. From the relative values of the cross sections for excitation of individual angular momentum states of the np5(n+1)p configurations, it is found that rotational coupling is the most important mechanism causing single excitation in the symmetrical systems Ne+Ne and Ar+Ar, and is also important, though not exclusively, for the other combinations studied.

Excitation of alkali atoms in collisions with molecules. Population of the states K(62S) and K(52-P)

Abstract Radiation at 4050 and 6930 A has been observed in collisions of fast potassium atoms with N 2 , O 2 , CO, NO, CO 2 , C 2 H 4 and C 6 H 6 . Emission at both wavelengths is weak compared to that at 7680 A. The threshold energy for emission at 6930 A has been found to be equal to the excitation energy (3.4 eV) of the state K(6 2 S) for N 2 and NO, but higher (5.5 eV) for CO.

Excitation in atom-atom collisions. K+Hg, K+K, and Na+K

Abstract Fast alkali beams produced by sputtering and charge exchange have been utilized to study collisional excitation of potassium atoms by mercury, potassium and sodium. K(4 2 P) was detected by its radiative decay. The threshold energies for excitation of K(4 2 P) are 4.0 eV for K+Hg. 1.6 eV for K+K, and 2.0 eV for Na+K. Cross sections are of the order of 3A 2 at 20 eV for all three systems.

Study of the optical emission in Ne+Ne and Ar+Ar collisions in the range 15 to 500 eV

Apparent threshold energies have been measured for excitation of states of the configurations Ne(2p53s), Ne(2p53p), Ar(3p54s) and Ar(3p54p). The energy dependence of the cross sections for emission of radiation due to the decay of these states has been determined up to about 500 eV. Estimates are given for the absolute values of the cross sections in this range. The cross sections for excitation of different states arising from the same configuration Ne(2p53p) or Ar(3p54p) have different energy dependence at low energies; regular structure is found in the cross section ratio Q(2p5 to 1s3)/Q(2p1 to 1s2) for Ne+Ne, and Q(2p4 to 1s3)/Q(2p1 to 1s2;2p5 to 1s4) for Ar+Ar.

A new system of oscillations in the potassium-rare gas scattering

Relative cross sections for the population of the fine-structure states 42P1/2 and 42P3/2 of potassium in collisions with Ar, Kr and Xe have been measured from threshold up to 600 eV lab. energy. The cross section ratio is found to be an oscillatory function of the inverse relative velocity. The area between the molecular states A2 Pi and B2 Sigma of the potassium-rare gas pairs was determined.