[susan53]

My initial reaction was they're the same, but looking at 40 examples of each from the Cobuild corpus, there does seem to be a difference in frquency of occurrence.

Both of them are used to modify noun phrases and clauses - here, I can't see much difference :

... the number of women in technology especially Asian women ...
try using powder alone-especially as new powder formulations are light
... of the cloud to the large-scale variable, particularly temperature and motion ...
Particularly as you'd done your four years


It's with adjectives and adverbs that there seems to be a difference. Although both can be used, out of the 80 total examples there were 16/40 examples of particularly + adj/adverb and only 3/40 of especially used in this way:

A lot of fun to keep 8 to 12 year-olds especially happy this Christmas.
home improvements will go especially well.
radical ideas are particularly welcome.
He is likely to do particularly well ...

In particular, when a noun phrase was composed of adj+noun, it was noticeable that pre-modification with especially modified the whole noun phrase:

But flats, especially high-rise flats
... the number of women in technology especially Asian women ...

whereas particularly often just intensified the adjective :

I thought he ran a particularly promising race
... his action constituted a particularly severe form of defeatism

I think in this use especially is probably less likely - though I wouldn't want to say that it can't be used. I suspect it's probably the most important difference though.

Hope that helps.