Speaker: Atandrita Bhattacharyya 

Topic: Conical Intersections and their Role in Initiating Visual Excitation 

Research Supervisor: Prof. Vivek Tiwari 

Date & Time: Thursday, 17 November 2022 at 4:00 PM 

Venue:  AG02/03, Chemical Sciences Building 


Born-Oppenheimer approximation is central to chemistry although its breakdown underpins vital ultrafast phenomenon such as rapid internal conversion between excite electronic states in photosynthesis and initiating vision. Since the discovery of the presence of geometric isomerism in the very first step of vision, scientific community were astounded merely by the rapid nature of this internal conversion and what physics might lead rapid internal conversion between electronic states on such timescales.

In my presentation, I will first talk about conical intersections, which exemplify breakdown of Born-Oppenheimer approximations to lead to efficient electronic funnels between adiabatic potentials. Then I will address how conical intersections play a critical role in the photo-isomerization of retinal, a molecule present in rod cells, eventually leading to visual sensation in our brains.




  1.        Malhado JP, Bearpark MJ, Hynes JT. Non-adiabatic dynamics close to conical intersections and the surface hopping perspective. Front Chem. 2014;2(NOV):1-21. doi:10.3389/fchem.2014.00097
  2.           Wang Q, Schoenlein RW, Peteanu LA, Mathies RA, Shank C V. Vibrationally coherent photochemistry in the femtosecond primary event of vision. Science ,1994;266(5184):422-424. doi:10.1126/science.7939680
  3.           Johnson PJM, Halpin A, Morizumi T, Prokhorenko VI, Ernst OP, Miller RJD. Local vibrational coherences drive the primary photochemistry of vision. Nat Chem. 2015;7(12):980-986. doi:10.1038/nchem.2398
  4.        Schnedermann C, Yang X, Liebel M, et al. Evidence for a vibrational phase-dependent isotope effect on the photochemistry of vision. Nat Chem. 2018;10(4):449-455. doi:10.1038/s41557-018-0014-y