1. Stark Effect and Torsional Motion Interaction in Biphenyl L. H. Coudert, a L. F. Pacios, b and J. Ortigoso c a LISA, CNRS/Paris 12 University, Créteil, France b ETSI Montes, Universidad Polytécnica de Madrid, Madrid, Spain c Iinstituto de Estructura de la Materia, CSIC, Serrano 121, Madrid, Spain

2. Overview The spectroscopy Stark interaction Alignment

3. Biphenyl is a non-rigid molecule The torsional angle 1 is 2  1. Merer and Watson, J. Mol. Spec. 47, 499 (1973) z x y

4. The potential energy function It has 90° periodicity

5. The potential energy function   eq.  Pacios and Gómez, Chem. Phys. Letters 432, 414 (2006)

6. Torsional energy levels Merer and Watson, J. Mol. Spec. 47, 499 (1973)

7. Stark interaction Hamiltonian

8. Polarizability tensor Coupling between E and the large amplitude motion Ramakrishna and Seideman, Phys. Rev. Letters 99, 103001 (2007)

9. Stark-rotation-torsion energy levels

10. Calculation I

11. Rigid case. 

12. Non-rigid case

13. Kumar, Gross, Safvan, Rajgara, and Mathur, Phys. Rev. A 53, 3098 (1996) E Alignment z Z The stark interaction energy is minimized

14. Calculation II

15. Rigid case. 

16. T  K. Intensity = 3.6 10 12 W·cm  << |   

17. Non-rigid case

18. T  K. Intensity = 3.6 10 12 W·cm  << |   

19. Laser Beam Alignment rigid case Z y x z  

20. Laser Beam Alignment non-rigid case Z y x z y x z      

21. Non-rigid case:  |    T  K. No laser

22. T  K. Intensity = 10 13 W·cm  Non-rigid case:  |   