Improvements in the generation and detection of Kr(3P) and Kr(3P2) atoms in a flow reactor: Decay constants in He buffer and total quenching rate constants for Xe, N2, CO, H2, CF4, and CH4

Abstract

The generation and decay of KrC P 2 ) and KrC Po ) atoms in a flowing afterglow reactor at 300 K using He carrier gas have been characterized and compared with Ar carrier gas. The dominant loss for the Kr( 3 P 2 ) and Kr( 3 Po ) atoms in He is diffusion to and quenching at the wall; the two-body quenching constants are of the order of 1 X 10 -15 cm 3 s -I for each. The KrC Po ) concentration in He carrier was sufficiently high that the total quenching rate constants were measured without resorting to optical pumping from the lower energy Kr( 3 P 2 ) state. Room temperature rate constants are reported and the product states are discussed for the KrCP 2 ) and KrCP o ) reactions with Xe, CO, N 2 , H 2 , CF 4 , and CH 4 ; the difference between the KrC Po) and KrC P 2 ) rate constants for N2 is nearly a factor of 6. Quenching rate constants for DCO are -25% smaller than those for IZCO. The KrC Po) reaction with CO gives mainly CO(b 3~ + ) and (e 3~ -); the CO(b, Vi = 0) level is much more rotationally excited than CO(h, Vi = 1). Excitation-transfer to Xe from KrCP z ) gives mainly Xe(6p[3/2Jz and [3/2] I ); the KrCP o ) reaction favors the Xe(7s) states. A systematic study of the best electrode configuration and operating conditions for the de discharge using He carrier gas is reported for the generation ofXeCP 2 ), NeCP o ) and NeCP z ), as well as KrCP z ) and KrCP o )' 3310

Excimer formation mechanism in gaseous krypton and Kr/N2 mixtures

“…To our knowledge, only three articles are devoted to the collisional quenching of krypton excited states [4,[19][20] by nitrogen. The quenching of the 3P 2 atomic levels is studied in [19][20] at low pressure of krypton (PI~ < 1 torr), giving a rate constant kq = 4.1(0.2)-10-12 cm 3 s-a.…”

“…Nitrogen is known as a weak quencher of excited krypton. The quenching rate constants of the 3P z atomic state and of the 1 u molecular one are known from literature [4,[19][20]. Nitrogen was used to check the validity of our model.…”

“…The quenching of the 3P 2 atomic levels is studied in [19][20] at low pressure of krypton (PI~ < 1 torr), giving a rate constant kq = 4.1(0.2)-10-12 cm 3 s-a. On the other hand, the study of the relaxed lowest excimer state 1~ quenching at high pressure (PKr = 800 tort), gives a much higher value of the twobody rate constant 7.65(0.34)-10-12 cm 3 s-1.…”

Conservation of the Kr+(2P1/2) state in the reactive quenching of Kr(5s′[1/2]) atoms by halogen-containing molecules

“…1 The high vibrational energy disposal, 2,3 state is the ratio of the KrX(D -X) to the KrX͑B -X and C -A͒ emission intensities. The results to be presented for Kr͑5sЈ͒ reactions 7,8 can be compared to reactions of Xe͑6sЈ͒ and Ar͑4sЈ͒ atoms. 9,10 Using the crossed molecular beam technique, Beijerinck and co-workers 11 studied the Kr͑5s͓3/2͔ 2 and 5sЈ͓1/2͔ 0 ͒ reactions with RBr molecules and their results will be compared to ours.…”

“…The subsequent Kr(5pЈ→5sЈ) radiative decay converted Ͼ40% of the Kr͑5s͓3/2͔ 2 ͒ atoms to the Kr͑5sЈ͓1/2͔ 0 ͒ level. 7,8 The total quenching rate constants, the KrX* product branching fractions, ⌫ KrX* , and the (B:C:D) product distributions will be reported from reactions ͑1͒ and ͑2͒ for 26 fluorine-, chlorine-, and bromine-containing reagents. Since KrI* is nearly totally predissociated, we studied only the HI reaction.…”