SB against unknown

[topspinner]

I have been trying to steal more from the SB, but keep running into situations like this.

Should you peel one off or just fold? When the Ace came I decided that I would donk bet it, to represent an Ace since I raised PF. I figured that If I checked, BB might check as well and then call the river. Since the pot is small, probably not the smartest play, just wanted to get others thoughts, as I am a little lost when I don't hit anything trying to steal from SB.

/2 Limit Holdem
6 players
Converted at weaktight.com

Stacks:
UTG (<font color="#0000cc">$58.50</font>)
UTG+1 (<font color="#0000cc">$91.25</font>)
CO (<font color="#0000cc">$34.50</font>)
BTN (<font color="#0000cc">$57.50</font>)
Hero (<font color="#0000cc">$63.50</font>)
BB (<font color="#0000cc">$73.00</font>)

Pre-flop: (1.5 SB, 6 players) Hero is SB T[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/club.gif[/img]
<font color="#777777">4 folds</font>, <font color="#cc0000">Hero raises</font>, BB calls

Flop: 6[img]/images/graemlins/spade.gif[/img] 5[img]/images/graemlins/heart.gif[/img] 5[img]/images/graemlins/spade.gif[/img] (4.0 SB, 2 players)
<font color="#cc0000">Hero bets</font>, <font color="#cc0000">BB raises</font>, Hero calls

Turn: A[img]/images/graemlins/club.gif[/img] (4.0 BB, 2 players)
<font color="#0000cc"> Hero (59.5)?</font>