A Rotational Analysis of Some C $S_{2}$ Bands in the Near Ultraviolet System

Six bands in the

λ 3100

system of C

S_{2}

, photographed in absorption on a 30-foot grating spectrograph, have been analyzed and

B

values are given for their initial and final states. The band structure is of the simple

PR

branch type, all of the observed bands originating from

{}^{1}Σ^{+}_{u} - {}^{1}Σ^{+}_{g}

transitions. The bands at

λ 3468

λ 3501

, and

λ 3535

originate in the normal state, giving a value

r_{0} = 1.548 A

for the normal carbon-sulphur separation. A partial vibrational analysis shows that for the bending vibration,

2 ν_{2}^{''} = 802

{cm}^{- 1}

. Two progressions,

v_{2}^{''} = 0

and

v_{2}^{''} = 2

, indicate that

ν_{2}^{'} = 270

{cm}^{- 1}

. Two bands,

λ 3501

and

λ 3601

, have their common upper

{}^{1}Σ^{+}_{u}

state perturbed by a

{}^{1}Π_{u}

state. A perturbation analysis gives constants which are in good agreement with observation and in addition gives the

B

value for the perturbing

{}^{1}Π_{u}

state. Evidence is presented which indicates that the excited electronic state of C

S_{2}

is bent. It is shown that, even if the molecule is bent to 125°, the

P

and

R

series may still be represented by a simple quadratic formula exactly as for a linear molecule, for

J

values less than 25. The state nomenclature used (

{}^{1}Σ^{+}_{u}

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A Rotational Analysis of Some CS2Bands in the Near Ultraviolet System