Hi,
As far as I know this is not possible as the trailing slash after main domain is handled by web browser. You can check for example that Chrome and FireFox don't display trailing slash after the main domain, but Internet Explorer does.
However, both ways are treated the same by the web server, because the HTTP request for main domain always uses / as the requested path.
According to Google itself (see
googlewebmastercentral.blogspot.co.uk/20...or-not-to-slash.html):
"Rest assured that for your root URL specifically,
example.com is equivalent to
example.com/ and can’t be redirected even if you’re Chuck Norris."