Physical Chemistry Third Edition

1000 23 Optical Spectroscopy and Photochemistry

dipole moments are roughly equal, and show the line

of maximum intensity.

d.Repeat part a, using the corrected energy levels. If you

have done Problems 23.64 and 23.65, use your

computer programs to calculate the reciprocal

wavelengths and intensities.

e.Draw a simulated infrared spectrum of the

fundamental band, assuming that the temperature is

298 K and using reciprocal centimeters as the

independent variable. Use the uncorrected energy

levels. Assume that the transition dipole moments are

roughly equal, and show the lines of maximum

intensity.

f.Repeat part c with corrected energy levels.

g.Draw a simulated rotational Raman spectrum of HF,

showing the Stokes lines. Assume that the temperature

is 298 K, and plot the Raman shift on the horizontal

axis, using reciprocal centimeters as the independent

variable. Use the uncorrected energy levels.

23.67Label each statement as either true or false. If a statement
is true only under special circumstances, label it as
false.
a.A forbidden transition cannot occur.
b.A forbidden transition always produces a weaker
spectral line than every allowed transition.
c.All forms of spectroscopy require that the radiation is
dispersed.
d.All molecules exhibit an absorption spectrum in some
part of the electromagnetic spectrum.

e.Any molecule that exhibits a rotational Raman

spectrum does not exhibit a microwave absorption

spectrum.

f.Any molecule that exhibits a vibrational Raman

spectrum does not exhibit an infrared absorption

spectrum.

g.Raman spectroscopy requires the use of a laser.

h.All infrared spectroscopy is absorption spectroscopy.

i.A nonpolar molecule cannot exhibit an infrared

spectrum.

j.A molecule that is a spherical top exhibits 3n− 6

vibrations that lead to infrared spectral lines.

k.A molecule that is a spherical top exhibits the same

kind of infrared spectrum as a heteronuclear diatomic

molecule.

l.Most organic substances are colorless in the visible

region and also do not absorb in the ultraviolet region.

m.A linear polyatomic molecule exhibits the same type

of infrared spectrum as a diatomic molecule.

n.A linear polyatomic molecule exhibits the same kind

of microwave spectrum as a diatomic molecule.

23.68Tell how you would distinguish between each pair of

substances, using spectroscopic techniques. If possible

specify two different techniques.

a.^1 H^35 Cl and^2 H^35 Cl

b.HC+CH and HC+CCl

c.^35 Cl 2 and^35 Cl^37 Cl