W. Mecklenbrauck

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.

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.

Electronic Excitation in Fast Collisions of Na with SO2 and NO2

A sputtered Na beam has been used to investigate collisionally induced electronic excitation in scattering with SO2 and NO2. Light from the radiative decay of excited electronic states was observed at several wavelengths, and measurements were made of the excitation cross sections as a function of the center‐of‐mass collision energy in the range 1–30 eV. In both scattering systems, the most intense light measured originated from the Na (32P→32S) D line. Light from the (42D→32P) Na transition was observed, but its intensity was more than an order of magnitude smaller than that of the D line. Emission also occurred from transitions with long radiative lifetimes (∼40 μsec). This emission is probably due to the B1→A1 molecular transitions of SO2 and NO2. The results have been discussed in terms of a potential curve‐crossing mechanism which seems to satisfactorily explain collisionally induced alkali atom excitation. For the molecular emission, an alternate mechanism has also been considered which involves vib...

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.

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.

Study of the optical emission in collisions between sodium and noble-gas atoms in the energy range between 10 and 500 eV

A complete set of data obtained from the collision-induced emission of the Na resonance lines is presented for Na-noble-gas collisions. The data include the emission cross sections and the polarisation fractions of the Na 32P3/2 to 32S1/2 resonance line, and the ratio of the cross sections for emission of the two resonance lines as a function of the collision energy, measured between the apparent thresholds and about 500 eV collision energy. Cross sections for ultraviolet emission by the noble-gas atoms have been measured in the same energy range. Except for Na-Ne, excitation of the noble-gas atom is relatively unimportant compared to the Na excitation. A qualitative interpretation of the results is attempted on the basis of molecular-orbital energy diagrams.

Excitation of the 42P3/2 level of potassium in collisions with rare gas atoms. Polarization of the emitted radiation

Polarization measurements have been performed on the K(42P3/2 to 42S1/2) line emitted after collisions between K and He, Ne, Ar, Kr and Xe. In all cases polarization is found in the studied lab energy range from 50-1500 eV; at low energies the polarization fraction is strongly dependent on collision energy. It is shown that the shape of the polarization function depends mainly on the relative population of the molecular states A2 Pi and B2 Sigma correlating with K(42P3/2)+rare gas (1S0).

Excitation in collisions between potassium and rare gas atoms

Accurate measurements of the threshold behaviour for excitation of the states K(42P12/) and K(42P32/) have been performed for K+Ar, Kr, and Xe. Emission due to the decay of excited rare gas states has been studied for the same systems between 50 and 250 eV. The results show that the simultaneous excitation of both potassium and rare gas atom is not important in populating K(42P). Excitation mechanisms are discussed on the basis of the molecular orbital model.

Excitation in collisions of potassium and sodium with pottassium. Measurements with separated doublet lines

Abstract Fast alkali beams have been utilized to study collisional excitation of potassium between 1.0 and 50 eV collision energy. The populations of the states 42P3/2 and 42P1/2 have been studied by measuring separately the transitions 2P3/2→2S1/2 and 2P1/2→2S1/2. The cross section for excitation of 42P3/2 relative to that for excitation of 42P1/2 is 1.25 for K + K; the cross section ratio decreases from 2.5 to 1.6 for Na + K with increasing collision energy.