随便选一个句子举例：我一拿到票就给你打电话：
1.once 最常用，I will call you once I get the ticket.
2.soon after，I will call you soon after I get the ticket.
3.
as soon as, I will call you as soon as I get the ticket
4.at once 其实也可以表达这个意思：
I will call you at once when I get the ticket.
5.at the very moment, 相当于soon after，
I will call you at the very moment I get the ticket
6.Immediately,相当于at once
I will call you immediately when I get the ticket.
7.还有好多像on/at+动名词形式的变态用法，基本上当作家的时候才能用到的句子。
哎呀妈呀，累死我了，写这么多字，给点分儿吧，不容易啊
补充：
其实都不常用，不知道为什要考试：
举一个on的用法，一般格式是on+动词ing形式，其实这个词归到这一类有些牵强，它更多是在表达“在某种情况下，发生了什么事情”翻译的时候习惯翻译成“一……就”，比如说“我一到上海就直奔客户那边去了”可以说成：
On reaching Shanghai,I went to the customer directly.
再举个at的用法，
At the news of her father’s death, she burst into tears. 一听到她父亲去世的消息她就哭了起来。
追问再弄点吧，我同学要十个词组一什么就什么