Absolute quenching cross sections of Hg(3P1) with various molecules

Abstract

Publication costs assisted by the U. S. Atomic Energy CommissionThe absolute quenching cross sections for Hg(3P1) with a number of quenching gases have been obtained in a steady-state photolytic experiment. The intensity of 2537-8, emission has been followed as a function of absorbed intensity, and also pressure of the quenching gas. Low Hg concentrations are maintained in order to avoid the complication of radiation imprisonment. Quenching rate constants are determined from modified Stern-Volmer plots. The results are compared to cross sections from Zemansky type experiments on a relative basis and in several cases to the absolute results of Yarwood, Strausz, and Gunning who applied Holstein theory to Zemansky type experimental results. Comparison is also made to other low opacity studies and, where possible, to the relative cross sections determined from chemical methods. Generally, good agreement is obtained. NO provides the only gross disagreement in these comparisons of the nine molecules studied. IntroductionThe quenching of the 3P1 state of mercury by a foreign gas represents probably the most extensively investigated and most useful primary photochemical system. The fundamental photophysical processes in this system are indicated in the following mechanism

Rate constants for the reactions of hydrogen atoms with some silanes and germanes

“…This is only approximately true because, as pointed out in the Experimental Section, the gases C2H4 and X can contribute up to about 5% of the total collisional deactivation of Hg)3?!). 45 It is easy to show that inclusion of collisional quenching by X and C2H4, with rate constants of k2 and k2, respectively, transforms (11) to (12), for our conditions of [H2]/[X] = [H2]/[S] = 98. l + i) + (12) Comparison of values of fe3//e4 calculated from (11) with those calculated from (12) using available quenching cross sections18, 45 shows that the maximum error introduced in the ratio by use of the simple expression is 2% and is 0 All experiments were carried out using an ionizing energy of 50 eV except for the isobutylene experiments which were done at 15 eV. 6 This value is taken as the average of the results of ref 47 usually less than 1 %.…”

Collision-Induced Fine-Structure Transitions of Hg(63P1 → 63P0) with N2 and CO. 2. Translational Energy Dependence

“…Numerous experimental studies have been performed to investigate quenching of photoexcited Hg(6 3 P 1 ) atoms by various molecules − and the quenching cross sections have been determined from attenuation of fluorescence at 253.7 nm (6 3 P 1 → 6 1 S 0 ) as a function of the pressure of target molecules. − An intramultiplet fine-structure transition, is one important pathway for the quenching of the Hg(6 3 P 1 ), because it produces metastable Hg(6 3 P 0 ), which can induce subsequential chemical reactions. − ,, Partial cross sections for this intramultiplet transition have also been measured for various gas targets at room temperature . Among them, intramultiplet transitions with two diatomic quenchers, N 2 and CO, attract special attention, because these two diatomic molecules are isoelectronic molecules with the same mass number and similar polarizability but the cross section for Hg−CO is about thirty times larger than that for Hg−N 2 , even though the main channel for the quenching of Hg(6 3 P 1 ) is this fine-structure process (1) for both of the Hg−N 2 and Hg−CO systems.…”

“…Numerous experimental studies have been performed to investigate quenching of photoexcited Hg(6 3 P 1 ) atoms by various molecules [1][2][3][4][5][6][7][8][9][10][11][12][13] and the quenching cross sections have been determined from attenuation of fluorescence at 253.7 nm (6 3 P 1 f 6 1 S 0 ) as a function of the pressure of target molecules. [1][2][3][4][5][6][7] An intramultiplet fine-structure transition, is one important pathway for the quenching of the Hg(6 3 P 1 ), because it produces metastable Hg(6 3 P 0 ), which can induce subsequential chemical reactions. [1][2][3]8,9 Partial cross sections for this intramultiplet transition have also been measured for various gas targets at room temperature.…”

Lyman‐α absorption photometry at high pressure and atom density kinetic results for H recombination

“…Experimental decay of H atoms was observed a t this pressure and a t successively decreasing pressures as the reaction cell was pumped out, in -70 torr increments. Note that sufficient Hz was present even at the smallest total pressures to ensure complete quenching of Hg (3P1) [16].…”