<h3>Title</h3>
<p><span style="color: #0000ff;">Interaction of Light with Matter: From Real to Virtual Photons</span></p>
<p><strong><span style="text-decoration: underline;">Abstract</span> :</strong></p>
<p>Light-matter interactions are perpetual sources of stimulation in experimental and theoretical sciences. Such interactions can involve real or virtual photons and examples of both cases will be presented. The first part of the talk will focus on the photo-physics of organic molecules. After excitation, among the various intramolecular processes, singlet-triplet intersystem crossing is an important channel both fundamentally and technologically. In organic chromophores, the quantum yield of intersystem crossing is often low due its spin forbidden nature. Strategies to enhance intersystem crossing such as heavy atom effect, molecular twist, and singlet fission in different core-twisted aromatic molecules will be presented and discussed.1-2<br />In the second part, an overview of the light-matter strong coupling will be presented where virtual photons (a.k.a. vacuum field) play a key role. In the strong coupling regime, hybrid light-matter states (polaritonic states), are formed by the interaction of a molecular transition with the electromagnetic field. The formation of such hybrid states results in the modification of various physical and chemical properties of the molecules/materials as it has been demonstrated over the past decade. 3-4</p>
<p><span style="text-decoration: underline;">References</span>:</p>
<p>1. Nagarajan, K.; Mallia, A. R.; Reddy, V. S.; Hariharan, M., Access to Triplet Excited State in Core-Twisted Perylenediimide. J. Phys. Chem. C 2016, 120, 8443-8450.<br />2. Nagarajan, K.; Mallia, A. R.; Muraleedharan, K.; Hariharan, M., Enhanced intersystem crossing in core-twisted aromatics. Chem. Sci. 2017, 8, 1776-1782.<br />3. Ebbesen, T. W., Hybrid Light–Matter States in a Molecular and Material Science Perspective. Acc. Chem. Res. 2016, 49, 2403-2412.<br />4. Nagarajan, K.; George, J.; Thomas, A.; Devaux, E.; Chervy, T.; Azzini, S.; Joseph, K.; Jouaiti, A.; Hosseini, M. W.; Kumar, A.; Genet, C.; Bartolo, N.; Ciuti, C.; Ebbesen, T. W., Conductivity and Photoconductivity of a P-Type Organic Semiconductor under Ultrastrong Coupling. ACS Nano 2020, 14, 10219-10225.</p>