1. 1 EFFECTS OF SPIN-ORBIT COUPLING ON THE SPIN- ROTATION INTERACTION IN THE AsH 2 RADICAL G. Duxbury 1 and Alex Alijah 2 1 Physics Department, University of Strathclyde, Glasgow, G4 0NG, UK 2 GSMA, UMR CNRS 6089, Universite de Reims Champagne-Ardenne, B.P. 1039, 51687 Reims Cedex2, France

2. 2 Outline of presentation Predissociation in the electronic spectrum of AsH 2 is dependent on the spin-orbit coupling parameter of the central atom. Making use of “Spectra and Dynamics of Diatomic Molecules”, ELSEVIER by H. Lefebvre-Brion and R.W. Field, one can appreciate the rapid increase of he magnitude of the spin-orbit constants in the di- hydrides NH 2, PH 2 and AsH 2. These range from 42.7 cm -1 for NH 2 to 191.3 cm -1 for PH 2 and to 1178 cm -1 for AsH 2. Effects may be seen via the change in separation of the R Q 0,N and P Q 1,N central sub-bands as the value of v 2 ’ increases, and the spectral lines themselves become more diffuse. The increase in the magnitude of the doublet splittings shows the effect of spin uncoupling, this becomes very apparent for higher values of K a ’.

3. Dixon, Duxbury and Lamberton (1968) Band Centres of the 0,v 2,0 -0,0,0 progression in the absorption spectrum of AsH 2 3

4. Diagrams for AsH 2 from SCIENCE IN CHINA PRESS www.scichina.com csb.scichina.com Dongfeng Zhao and Yang Chen Start of predissociation Predissociation increases

5. Dongfeng Zhao and Yang Chen Predissociation visible Predissociation effects large

6. Predissociation effects very large Last band visible Dongfeng Zhao and Yang Ch

7. 7 Spin-rotation interaction with Hund’s Case a.

8. 8 Comparison of Hund’s cases (b) and (a)

9. Diagrams for AsH 2 Spin uncoupling AsH 2 9

10. AsH 2 spin uncoupling, v 2 ’= 2 and v 2 ’= 3 10

11. 11 References 1 Dixon,R.N, Duxbury, G. and Lamberton, H.M., Proc. Roy. Soc. A. 305, 271-290 (1968) 2 Duxbury, McDonald, Van Gogh, Alijah, Jungen and Palivan, J.Chem Phys 108, 2336, (1998) 3 Alijah, A. and Duxbury, G. J. Mol. Spectrosc. 211, 1 (2002) 4 Duxbury, G. and Reid, J.P. Mol. Phys. 105, 1603 (2007) 5 He, S-G. and Clouthier, D.J. J. Chem. Phys. 126, 154312 (2007) 6 Zhao, D, Qin, C. Ji, M. Zhang, Q and Chen, Y. J. Mol. Spectrosc. 256, 192-197 (2009) 7 Alekseyev, A.B., Bunker, R.J. and Lieberman, H-P J. Chem. Phys. 135,244303 (2011) 8 Grimminger, R.A. and Clouthier, D.J. J. Chem. Phys. 137, 224307 (2012)