Hampshire 194 for 5 (Dawson 51*) beat Scotland 192 for 7 (Mommsen 60*) by five wicketsScorecard Holders Hampshire survived a spirited Scotland challenge to win by five wickets and secure their second Yorkshire Bank 40 victory in three days.
After winning the toss and being put in to bat, Saltires openers Calum MacLeod and Freddie Coleman added 37 runs inside five overs. But the loss of MacLeod for 13, caught at short fine leg by Chris Wood off David Balcombe, sparked a mini collapse which slowed the Scots' innings to a standstill.
Coleman, after 27, was next to fall, Hamza Riazuddin striking in his first over to leave Scotland on 49 for 2. Matt Machan went soon after for 8, caught by Sean Ervine at midwicket to give Balcombe - playing his first list A game for Hampshire since 2009 - his second wicket of the day.
Ervine became the second Hampshire bowler to strike in his first over, forcing Majid Haq to top-edge tamely to Liam Dawson at slip for just 5.
Richie Berrington and skipper Preston Mommsen combined to briefly stem the loss of wickets, but their partnership ended when Berrington was stumped off the bowling of Danny Briggs for 19 to leave Scotland floundering on 88 for 5 in the 23rd over.
Wicketkeeper Matthew Cross, on debut, added 43 with his captain, before holing out to James Vince off the bowling of Wood for 21. And Wood struck again a short while later, Briggs catching Moneeb Iqbal for a breezy 17 from 12 deliveries.
A hard-hitting cameo from Gordon Goudie, 15 from five balls, helped Scotland add 33 runs in the last two overs, as the visitors ended on 192 for 7, skipper Mommsen top scoring with 60 not out.
The total looked at least 20 runs light on an excellent batting track against an in-form Hampshire batting line-up, but the home side were soon in trouble. Michael Carberry edged Calvin Burnett behind in the third over, before opening partner Vince was caught by Haq off the bowling of Goudie.
And when George Bailey was bowled by Gordon Drummond for 24, Hampshire looked in real danger at 61 for 3 in the 15th over. It got worse for Hampshire just two overs later when Ervine hit offspinner Machan straight to mid-on to leave the hosts 78 for 4, and falling behind the required run-rate.
Captain Jimmy Adams steadied the ship in partnership with Liam Dawson, but when the former fell for 51, Hampshire hopes lay in the balance at 130 for 5.
But the prospect of an embarrassing defeat was averted by Dawson, 54 from 62 balls, and keeper Adam Wheater, 35 from 32 balls, who batted without alarm to secure the win.