Problems

12.1  What are selection rules? Distinguish between the selection rules of electronic spectra of atoms and
       diatomic molecules.

12.2  Convert  the wavelength/energy data given in Table 12.1 into electron volts and cm^-1. 
         Use 1 ev  = 8066 cm^-1 and 1 ev  = 96.6 kJ/mol.

12.3  If the life time of an excited state is 10^-9s,  what is uncertainity in its energy?  What is the spread in its
        frequency or the width of the spectral line?

12.4  If  ∆E  = 0.1 kJ/mol between the ground state and the first excited state, what is the population of this
        excited state at 300 K if the ground state has 10²³ molecules?.

12.5  What is the reason for the yellow doublet in the spectrum of sodium vapor?

12.6  What are the first three transitions in the electronic spectrum of H₂ ?

12.7 The – C  = C -  and the – C  = O groups have π → π* transitions at 170 and 166 nm respectively.  If both        these molecules have adjacent Cl and OCH₃ groups, at what wavelengths do you expect the peaks of the
         π → π* transitions? A Cl group shifts the peak by 5 nm and an OCH₃ group  by 6 nm.

12.8  Rationalize the differences between absorption spectroscopy and emission spectroscopy.