Development of a stable source of atomic oxygen with a pulsed high-voltage discharge and its application to crossed-beam reactions

Abstract

To investigate the reactions of oxygen atoms with ethene and silane in a crossed-beam condition, we developed a stable, highly intense, and short-pulsed source of atomic oxygen with a transient high-voltage discharge. Mixtures of O(2) and He served as discharge media. Utilizing a crossed molecular-beam apparatus and direct vacuum-ultraviolet ionization, we measured the temporal profiles of oxygen atoms and the time-of-flight spectra of reaction products. With O(2) 3% seeded in He as a discharge medium, oxygen atoms might have a full width as small as 13.5 micros at half maximum at a location 193 mm downstream from the discharge region. Most population of oxygen atoms is in the ground state (3)P but some in the first excited state (1)D, depending on the concentration of precursor O(2). This discharge device analogously generates carbon, nitrogen, and fluorine atoms from precursors CO, N(2), and F(2), respectively.

Formation of Polyynes C4H2, C6H2, C8H2, and C10H2 from Reactions of C2H, C4H, C6H, and C8H Radicals with C2H2

“…In the present work, the title reactions were investigated in a crossed-molecular-beam quadrupole-mass apparatus [16][17][18] by measuring time-of-flight (TOF) and photoionizationefficiency (PIE) spectra of products with synchrotron vacuum-ultraviolet (VUV) light. One source chamber served to generate a pulsed beam of C 2n H radicals from 1% C 2 H 2 /He by discharge 19 and the other source chamber served to generate a pulsed beam of 5% C 2 H 2 /He. The yield of a discharge product that has a mass larger than 100 u or contains more than three 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 hydrogen atoms is negligibly small ( Figure S1 in the Supporting Information).…”

Formation of C9H2 and C10H2 from Reactions C3H + C6H2 and C4H + C6H2

“…The reactions of C 3 H and C 4 H radicals with C 6 H 2 were carried out in a rotating-source-assembly crossed-molecular-beam apparatus that had been described elsewhere. − Thus, only a brief description is given here. One source chamber equipped with an Even–Lavie valve and a discharge device served to generate a pulsed beam of C 3 H or C 4 H radicals (hereafter designated as primary beam) from a mixture of 1% C 2 H 2 seeded in He with a stagnation pressure 105 psia. The pulse of C 3 H (C 4 H) radicals had a most-probable speed of 1890 (1875) m s –1 and a speed ratio greater than 7.…”

Exploring the dynamics of C/H and C/Cl exchanges in the C(3P) + C2H3Cl reaction

“…One source chamber was equipped with a solenoid valve (Even-Lavie type) and a discharge device 22 to generate a pulsed beam of carbon atoms from a mixture of 10% CO seeded in helium at a stagnation pressure of 105 psia. Carbon atoms were characterized to be populated exclusively on the ground state 3 P via the measurement of photoionization spectra of carbon atoms; 15 the population on the first electronic excited state 1 D is negligible.…”