The energy of the excited state dynamics of a molecule is closely related to its molecular geometry. When a molecule absorbs a photon, it gets excited from its ground state to a higher energy state. This process leads to changes in the electronic configuration and, consequently, the molecular geometry. The relationship between the energy of the excited state and the molecular geometry can be understood through the following factors:1. Bond lengths and angles: In the excited state, bond lengths and angles can change due to the redistribution of electron density. This change in geometry can lead to either stabilization or destabilization of the excited state, depending on the specific molecule and its electronic configuration.2. Conical intersections: When two or more potential energy surfaces PES of different electronic states intersect, it is called a conical intersection. At these points, the energy gap between the states becomes very small, and non-adiabatic transitions between the states can occur. The molecular geometry plays a crucial role in determining the location and properties of conical intersections, which in turn influence the excited state dynamics and energy.3. Vibronic coupling: The interaction between electronic and vibrational motions in a molecule is called vibronic coupling. This coupling can lead to changes in the energy levels of the excited state and is highly dependent on the molecular geometry.Ab initio calculations, which are based on first principles quantum mechanics, can be utilized to predict the behavior of the excited state dynamics as a function of molecular geometry. These calculations involve solving the Schrödinger equation for the molecular system to obtain the electronic wavefunctions and energies. By performing ab initio calculations, one can obtain the following information:1. Potential energy surfaces: Ab initio calculations can provide the PES for different electronic states of a molecule. By analyzing these surfaces, one can understand the relationship between the molecular geometry and the energy of the excited states.2. Transition dipole moments: These calculations can also provide the transition dipole moments between different electronic states, which are essential for understanding the absorption and emission spectra of a molecule. The transition dipole moments are sensitive to the molecular geometry and can help predict the changes in the energy of the excited state dynamics.3. Conical intersections and non-adiabatic couplings: Ab initio calculations can help locate conical intersections and determine the non-adiabatic couplings between different electronic states. This information is crucial for understanding the excited state dynamics and the role of molecular geometry in these processes.4. Vibronic coupling constants: By performing ab initio calculations, one can obtain the vibronic coupling constants, which provide information about the interaction between electronic and vibrational motions in a molecule. This information can be used to understand the influence of molecular geometry on the energy of the excited state dynamics.In summary, the energy of the excited state dynamics of a molecule is closely related to its molecular geometry, and ab initio calculations can be utilized to predict this behavior. By obtaining information about potential energy surfaces, transition dipole moments, conical intersections, and vibronic coupling constants, one can gain insights into the relationship between molecular geometry and the energy of the excited state dynamics.