BUG: .str.split() method of pandas.Series behaves strangely

[oltip]

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the master branch of pandas.

Reproducible Example

import pandas as pd 

series = pd.Series(['bae systems (international) ltd']) 

series.str.split('a. s.')  
# returns 
0    [b, stems (international) ltd]

Issue Description

The .str.split() method of Pandas Series does not split items as expected.

Expected Behavior

The .str method of Pandas Series does not split items as expected.

s = "bae systems (international) ltd"
s.split('a. s.')

# should return
['bae systems (international) ltd']

Installed Versions

pandas 1.3.0

[mzeitlin11]

Thanks @oltip for the report. Going to close as a duplicate of #43563 - the problem is that an argument of length > 1 is interpreted as a regex. So escaping the periods would be one potential workaround