1. Consider a water molecule in the gas phase. a) What is the point group of water? b) The ground electronic state of water has Ai symmetry. What are the possible irreducible representations (irreps) for optically allowed excited electronic states? Would electronic transitions to the triplet states be allowed? c) Can water be observed by IR spectroscopy (remember to justify your answer)? Solution a) water is having C2 axis of principle and two vertical planes which contains the principle axis of rotation which is C2. In short we have only three symmetry elements such that identity element E, principle axis of rotation C2 and two vertical planes.so water molecule in gas phase will have C2V point group symmetry. C) yes we can observe infrared spectra for water because of the different stretching and bending vibrations of elastic bonds.we observe different peaks for water molecule for o-H bond stretch and bend... .

1. 1. Consider a water molecule in the gas phase. a) What is the point group of water? b) The
ground electronic state of water has Ai symmetry. What are the possible irreducible
representations (irreps) for optically allowed excited electronic states? Would electronic
transitions to the triplet states be allowed? c) Can water be observed by IR spectroscopy
(remember to justify your answer)?
Solution
a) water is having C2 axis of principle and two vertical planes which contains the principle axis
of rotation which is C2. In short we have only three symmetry elements such that identity
element E, principle axis of rotation C2 and two vertical planes.so water molecule in gas phase
will have C2V point group symmetry.
C) yes we can observe infrared spectra for water because of the different stretching and bending
vibrations of elastic bonds.we observe different peaks for water molecule for o-H bond stretch
and bend...