Energies of Spectral Transitions (5)

Question 1

What energies are involved in rotational transitions?

Answer 1

0-100 cm-1

Question 2

What energies are involved in vibrational transitions?

Answer 2

0-3000 cm-1

Question 3

What energies are involved in electronic transitions?

Answer 3

10,000-50,000 cm-1
large, UV-Vis

Question 4

What is the approximate order of magnitude for transition energies?

Answer 4

ΔEe ≈ ΔEv x 10-10^2 ≈ ΔEr x 10^4

Question 5

What are the selection rules for electronic spectroscopy?

Answer 5

all molecules

Question 6

What are the selection rules for rotational spectroscopy?

Answer 6

permanent electric dipole moment

Question 7

What are the selection rules for vibrational spectroscopy?

Answer 7

permanent change in dipole moment for IR or deformation of overall polarizability of electron cloud during Raman

Question 8

Why are vibrational and rotational transitions also seen in electronic spectra?

Answer 8

because energy of electronic transitions is so large, they are excited by electronic energy transitions

Question 9

Why do these transitions appear mostly in gas phase electronic spectra?

Answer 9

broad absorption band for small molecules in gas phase have a lot of rotational/vibrational fine structures. Vibrational are coarse and rotational are fine molecules at the top.