Dear alicevideira:
 
 �Can we use "no sooner" without "than"? Is it grammatically correct? �
 
I cannot think of a suitable example where  �than � is NOT used.
 
Randolph Quirk, in "A Comprehensive Grammar of the English Language", page 999.
 
"Correlative Subordinators = [ �pairs of linking words �]"
 �no sooner ... than ... �
 �no sooner ... when ... � (informal)
 
So, according to Quirk,  �No sooner ... when ... � can be used INFORMALLY.
But, I don �t ever recall hearing it used like this!
 
Page 1001 
 �no sooner ... than �
 
 �barely/hardly/scarcely ... when/before �
  
"There is a traditional objection to the use of when as correlative with no sooner and to the use of than as correlative with the three negative adverbs."
 
In other words:
 
 �No sooner ... than ... � = OK
 �No sooner ... when ... � NOT OK.
 
 �Barely ... when ...  � = OK.
 �Hardly ... when ...  � = OK.
 �Scarcely ... when ...  � = OK. 
 
 �Barely ... before ...  � = OK.
 �Hardly ... before ...  � = OK.
 �Scarcely ... before ...  � = OK. 
 �Barely ... than ...  � = NOT OK.
 �Hardly ... than ...  � = NOT OK.
 �Scarcely ... than ...  � = NOT OK.
 
Page 1005:
"There is a stereotyped construction:"
"No sooner said than done!" OK
"It was no sooner said than done!" OK
 
I hope that I have helped you.
 
Les Douglas