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This book represents principles and concepts in types of spectra in molecules especially in diatomic molecules and explains the molecular physics, especially, I think this work useful for a third and fourth year undergraduate course in college of science. It presents concepts to an understanding of structure for molecules, it gives an important topics for student´s interest has been assigned as a supplement and together offer an excellent grounding for students interested in graduate work, whether in this area or some other. Indeed, most of the students taking this course have gone on to study other areas of physics.

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Dr. Adil Nameh Ayyash. B.Sc Physics, Collage of Science, University of Anbar, Anbar, Iraq, 2001. M Sc.In 2004 and Ph.D. In 2014 Dep. of Physics, Collage of Science, AL-Mustansiriyah University, Baghdad, Iraq.He studied (Spectra and Molecular Physics, materials science). He published many papers in different international scientific journals.

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