file.exists does not like path names ending in /

If a path name ends in slash then file.exists says it does not exist.
I would have expected these to all return TRUE.

file.exists("/Program Files")

[1] TRUE

file.exists("/Program Files/")

[1] FALSE

file.exists(normalizePath("/Program Files/"))

[1] FALSE

R.version.string

[1] "R version 3.0.2 Patched (2013-11-25 r64299)"

I am using Windows 8.1 .

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