Can anyone please tell me the exact difference between すぐに and すぐさま?
- すぐに is far more common. In BCCWJ there are more than 13000 examples of すぐに (excluding examples of まっすぐに), while there are only 685 examples of すぐさま.
- すぐさま sounds more literary and emphatic. In conversation すぐさま is rarely used.
- This is not a strict rule, but すぐさま tends to refer to something more immediate. For example, 薬を飲めばすぐに効果が現れる can mean the medicine takes effect in a few hours or even days (as long as the speaker feels it's quick), but 薬を飲めばすぐさま効果が現れる would usually mean it takes effect in no longer than an hour.
- すぐ is also a noun that works as a so-called no-adjective. You can say イベントはもうすぐだ, すぐの出発, and so on.