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# LASER: ATOMIC TRANSITION OR ELECTRONIC TRANSITION

I start this topic with the concept of the absorption and emission first of all  where one use the Atomic Excitation or Electronic Excitation

What do you think when a photon strike on the electron? Does this result gives of transfer of electron in higher energy state that is represented by either electronic transition (ET) or the atomic transition (AT). Now doubt, which one is correct (ET or AT)?  Yes, both are true. Now, in reference to the atomic process perspective there are two different states, one is ground and second is the excited state. These states are reflection of existed electrons, orientation in different states which are filled according to the Pauli exclusion rule, distributed in orbitals through Hunds and Aufbau rules and principle, respectively.  Any change, in electronic configuration means change in atomic states, here ground state means electrons are in defined states and distributed as per the above mentioned rules. When an electron absorbs the energy and goes into the higher state electronic configuration changes that you can see and this transition of electron from lower state to the higher state is known as electronic transition.

On the other hand, the same process in atom perspective is represented by the excited state of the atom (jumps of electron in higher state). So both electronic and atomic transitions are compliment to each other. In last, atomic transition represent the change in the states of atom i.e., from ground state to the excited state and then after ground state. In real, electrons absorb/emits the energy and stay in a particular state of the atom (not a solid quantity, as per the Bohr’s and Somerfield’s atomic model, electron revolves around the nucleus with definite energy) for defined time that is known as life time of the atomic state.  Hence ground and excited states of the atom are the result of electronic distributions in various states of atom. Whether you use atomic transition or electronic transitions the concept behind of it should be clear and both are true for LASER explanation.

#### Dr Sushil Kumar

Dr. Sushil Kumar, a physicist, an eminent researcher and a teacher for the benefit of students and fellow physicists alike. Vyom Hans is an effort to create a better platform and also to help the students to be able to have content at their hands whenever they want, online. Dr. Sushil continues to upload his lectures and post articles about latest researches in physics, academic, physics education, and also lessons about daily life and how physics define every aspect of our everyday movement and life.