Formation and Emission Spectra of C2 Swan Bands during the Reaction of Laser Ablation Al Plume with CF4,CCl4 and CH2Br2 Beams
ZHANG Shu-dong1, 2, LI Hai-yang1*
1. Laboratory of Environmental Spectroscopy, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences,Hefei 230031, China 2. Physics and Electronic Engineering College, Northwest Normal University, Lanzhou 730070, China
Abstract:The emission spectra of C2 Swan bands transition were observed in 430-600 nm region by Q-switched laser ablation target of Al reacting with CF4,CCl4 and CH2Br2 beams. Five vibration band sequences (Δv=2,1,0,-1 and -2) of d3Πg-a3Πg were identified and the largest vibration number of excited state d is 6. Using a local thermal equilibrium model, the vibrational temperature of d state was determined to be about 6 000 K. Meanwhile, some bumps, separated by about 0.3 nm, were observed between vibrational bands of Δv=0 and -1 sequences, which were due to accidental and periodical accumulations of rotational lines belonging to several vibrational bands. The formation mechanism of excited C2d3Πg state is considered as when laser induced Al plasma expansion in the background reaction gas sample, the collisions between metal particles and gas sample molecules cause the dissociation of precursors, so atomic C is produced. Meanwhile, the shock wave induced by plasma expansion might cause molecules dissociation as well. Then C atoms combine to form C2 in the ground state X1Σ+g(Te=0 cm-1) or first excited state a3Πu(Te=716 cm-1). The electronic energy transfer between excited state Al (2S1/2)(Te=25 348 cm-1) and C2a3Πu state produces the excited state d3Πg(Te=20 022 cm-1). Another mechanism that may be possible is that b3Σ-g state of C2 is produced first, then undergoes a radiationless transition into d3Πg state through crossing with the d3Πg,v′=6 level. But the vibrational population of v′<6 levels is formed by collision relaxation.
张树东1, 2,李海洋1*. 激光烧蚀Al热原子与CF4,CCl4, CH2Br2反应中激发态C2的形成 [J]. 光谱学与光谱分析, 2004, 24(11): 1281-1284.
ZHANG Shu-dong1, 2, LI Hai-yang1*. Formation and Emission Spectra of C2 Swan Bands during the Reaction of Laser Ablation Al Plume with CF4,CCl4 and CH2Br2 Beams . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2004, 24(11): 1281-1284.
[1] Riju C Issac, Pillai K Vasudevan, Harilal S S et al. Appl. Surf. Sci.,1998,125:227. [2] Jin J, Ran Q, Zhang X P, Chen Y,Chen C X. Chinese Phys.,2002,11:481. [3] Sugana M, Kasuya A, Tohji K et al. Chem. Phys. Lett.,1998,292:577. [4] Zhang H Y, Chen K X, Zhu Y J et al(张海燕,陈可心,朱燕娟等). Acta Phys. Sinica(物理学报), 2002,51:444. [5] Harilal S S, Issac Riju C, Bindhu C V et al. J. Phys. D: Appl. Phys., 1997,30:1703. [6] Burakov V S, Tarasenko N V,Savastenko N A. Spectrochimica Acta(Part B),2001,56:961. [7] Li Y D, Qian Y T, Liao H W et al. Science, 1998, 281: 246. [8] Zhang S D, Li H Y(张树东,李海洋). Acta Phys. Sinica(物理学报),2003,52:1297. [9] Zhang S D, Zhang W J(张树东,张为俊). J. Atom Mol. Phys.(原子与分子物理学报), 2001,18:159. [10] Zhang S D, Zhang W J(张树东,张为俊). Acta Phys. Sinica(物理学报),2001,50:1512. [11] Zhang S D, Chen G Y(张树东,陈冠英). Nuc. Phys. Rev.(原子核物理评论),2002,19:200. [12] LI Xue-chu(李学初). Science in China(中国科学), 1981,11:1497.