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

Overview The spectroscopy Stark interaction Alignment

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

The potential energy function It has 90° periodicity

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

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

Stark interaction Hamiltonian

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

Stark-rotation-torsion energy levels

Calculation I

Rigid case. 

Non-rigid case

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

Calculation II

Rigid case. 

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

Non-rigid case

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

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

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

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

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