Acta Phys. -Chim. Sin. ›› 1988, Vol. 4 ›› Issue (04): 387-392.doi: 10.3866/PKU.WHXB19880412

• ARTICLE • Previous Articles     Next Articles

DYNAMICS OF THE CHEMILUMINESCENT REACTIONS OF Ba+Cl2, Br2—FORMATION MECHANISM OF THE ELECTRONICALLY EXCITED BaCl2*

Lü Richang; Li Fue; Li Jian; Peng Lianshun; Liu Haisheng; He Guozhong; Lou Nanquan   

  1. Dalian Institute of Chemical Physics; Chinese Academy of Sciences
  • Received:1986-11-04 Revised:1987-07-07 Published:1988-08-15
  • Contact:

PDF

2274

Like

Abstract: The chemiluminescent reactions of Ba+Cl_2, Br_2 were carried out in a beamgas apparatus and the CL spectra have been observed. The continuum in the visible region of the CL spectrum has been asigned as the emission of BaCl_2~*, but there is a discrepancy about the mechanism of formation of BaCl_2~*. The observed quadratic dependences of the BaCl_2~* intensity on Cl_2 pressure (Fig.1), the Ba intensity upon the Ba atom number density (Fig.3) and the independence of the BaCl_2~* emission upon the Ba atom number density in the high density region (Fig.2) imply that the two body recombination radiation or the dimmer Ba_2 exchange reaction Ba_2+Cl_2 should be neglected. No enhancement but a slight drop of the BaCl_2~* intensity with increasing N_2 mixed with Cl_2 indicates that the three body stabilization route can be excluded as well.
The fact that the BaCl_2~* intensity increases along the Ba beam axis from the entrance as measured by OMA (Fig.5) is an evidence against the rule of single collision reaction radiation in a beam-gas regime. From the above consideration the following reaction processes for the formation of BaCl_2~* are proposed:
Ba+Cl_2 ~(k_1)—— BaCl~≠+Cl (1)
BaCl~≠+Cl_2 ~（k_2)—— BaCl_2~*+Cl (2)
BaCl~≠+Ba ~(k_3)—— BaCl+Ba~* (3)
BaCl_2~* ~(k_4)—— BaCl_2+hν′ (4)
Ba~* (k_5)—— Ba+hν′ (5)
where the superscripts≠and * denote the vibrationally highly excited ground state and electronically excited state respectively.
The kinetic analysis shows that the two step reaction mechanism for the formation of BaCl_2~* represented by the above elementary processes is reasonable. The computer simulations. as shown in Figures 1, 2 and 5, are well in agreement with the experimental observations.
The same experiments and discussion have been done ofr the reaction Ba+Br_2. The dynamics of the reaction Ba+Br_2 is similar to that of Ba+Cl_2. We have found that the CL intensity of BaBr_2~* is weaker but spreader than that of BaCl_2~* (Fig.6). A discussion about the CL spreading and an argument on the life time of the emitter BaCl_2~* are presented.