Mr Mundell also describes the Scottish Government's position on Nato membership as "absolutely incoherent".
He said that if an independent Scotland did not sign up to the organisation's nuclear strategic concept, then "it won't be in Nato; that's the reality".
His remarks come after the First Minister last night described how an independent Scotland would become the "Northern Light" to the "dark star" of London, rebalancing the economy away from the UK capital, which sucks in resources, people and energy.
In his speech, given just yards from the Treasury nerve-centre, which is co-ordinating the UK Government's push against independence, Mr Salmond also made a personal declaration.
He said: "I believe we'll win; I've got that feeling in my bones. I also know, absolutely for certainty, that we will fight that campaign in such a way that when we look back, we'll say that campaign itself made the country a better, more engaged, progressive place."
Mr Salmond said the referendum was "about the people of Scotland" and not about politicians or David Bowie, who voiced his support for Scotland to remain part of the UK at this year's Brit Awards.
Shadow Scots Secretary Margaret Curran said: "Alex Salmond can't hide the fact he still can't give Scots an answer on the most fundamental question about our future; what currency we would be using. He's willing to risk higher costs for the weekly shop and higher interest rates for Scots' mortgages. Instead of lectures in London, we need answers on the future of the pound in our pocket."
In an interview with The Herald, Mr Mundell makes clear the Scottish Conservatives will not repeat the mistakes of the past on devolution and, in the event of a No vote, points to a Calman Mark II process following next year's General Election to agree additional powers for the Scottish Parliament post 2016.
On further devolution he says: "Clearly, there's scope in relation to income tax. We don't want to rule out anything in relation to non-financial powers. We should be in the van- guard of propos- ing as much devolution and fiscal authority to local government as we can" but it is very unlikely we will go down the route of corporation tax".
The 51-year-old, who next year will mark 10 years as the only Tory MP in Scotland, says, if there is a Yes vote, the First Minister's declaration of Independence Day will have no legal status and be merely an aspiration.
"It is only achievable if he was willing to make huge concessions on what his position is. Either he is immediately going to throw the towel in on a whole range of issues or it is simply not achievable," declares Mr Mundell.
He added: "It's going to be more than 18 months if there is going to be meaningful negotiation on significant issues."
Last month, a row broke out after a senior UK Government source insisted a Yes vote alone would not deliver independence; Scotland would not break away from the UK until a full deal was negotiated.
When pressed about Mr Salmond's 2016 date for independence, Mr Mundell stressed: "But that has no legal status; it's an aspiration … in the real world, you can't proceed on the basis of assertion because other people have their own interests and they are not going to play ball."
As Tory grandee Lord Strathclyde puts the finishing touches to his review of the Scottish Conservatives' approach on further devolution, due to be published in late May, Mr Mundell makes clear his party will "not be bystanders".
The Dumfriesshire, Clydesdale and Tweeddale MP said: "We will be there and will have an offering on the table. What we are not saying is that we are going to persevere with our offering if that is not acceptable to others within Scotland.
"We are not going to enforce our settlement; we want to work with others to get an agreed settlement."