Question

In a rotational spectra 10th and 11th line are separated by spacing 20 cm-1 .What is the value of rotational constant in cm-1
​

Answer 1

The rotational constant is related to the bond length R by the equation:

˜

B

=

h

8π2cμR2

with the reduced mass μ=

mCmO

mC+mO

=1.14×10−26kg

Therefore, the bond lengths R0 and R1 are:

R

2

0

=

h

8π2cμ

˜

B

0

=1.27×10−20m2

R0=1.13Å

R

2

1

=

h

8π2cμ

˜

B

1

=1.52×10−20m2

R1=1.23Å

The internuclear distance change as a result of this transition is:

R1−R0=0.1Å