National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 22May 2022
NIST Standard Reference Database 101
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VII.D.3.

Converting between rotational constants and moments of inertia

Rotational constants are inversely related to moments of inertia:

B = h/(8 π2 c I)

Where B is the rotational constant (cm-1)
h is Plancks constant (gm cm2/sec)
c is the speed of light (cm/sec)
I is the moment of inertia (gm cm2)

Enter a rotational constant or a moment of inertia in the appropriate box below and press the adjacent calculate button. The related quantities will appear in the other boxes.

B cm-1
B GHz
B MHz
 
I gm cm2
I amu Å2