Vibration-rotation spectrum of hydrogen chloride

From the lines in the vibrational-rotational fundamental of H C1 to determine its moment of inertia in the ground vibrational state and in the first excited vibrational state. 

The wave-numbers a of lines measured (Mills, Thompson, and Williams, Proc. Roy. Soc. A1953,218, 29) in the fundamental vibration band of H C1 are given in table 1 

The term levels expressed in wave-numbers axe related to the rotational quantum number / as follows. In the ground vibrational state 

The selection rules are J - -J — 1 referred to as the P J) line with J 1 OT J — 1— 7 referred to as the R(J — 1) line with J 1. According to this accepted notation there is an i (0) line but no P(0) line. Consequently absorption lines exist with fte following wave-numbers 

We see immediately by inspection that the gap occtns between the wave-numbers 2865.1 cm and 2906.2 cm. We then construct table 2. 

---