Humans try to help aliens deactivate their defensive barrier

Question

I read this short story in the 90s, it was in either a magazine or an anthology and probably written much earlier.

Humans were expanding in space and found a race of friendly aliens. Meeting them directly was impossible because the aliens had previously built a barrier around "their" space that no ship could pass, in either direction. It had been a precaution after an historical war with a very aggressive third race.

The barrier was something like a Star Trek shield, maintained by a generator on the aliens' side, but the aliens were unable to deactivate it. They told the humans how it worked and invited them to try to remove it.

A shipload of humans set off, carrying several scientists with different ideas for how the barrier could be defeated. There was also an arrogant captain and a "crew girl", who the narrator/protagonist described as being so skeptical about everything that she could make a man doubt his own name. She didn't do much for his confidence in his shield-busting idea.

Towards the end, the captain proved to the protagonist that he'd made an error in his calculations and his idea couldn't work.

He similarly quashed all the other scientists' ideas, then revealed that the crew girl was the real answer: the barrier relied on a (quantum?) effect that could be affected by observers, and her extreme skepticism disabled the whole thing long enough for them to plant a large bomb on the generator. I don't remember why the scientists were taken along.

Answer 1

The Pod in the Barrier by Theodore Sturgeon.

The girl is Virginia. The quote you remember is:

He said, “What we did, we found Virginia trying to commit suicide. She had this doubt thing on her back, naturally. She didn’t want to go on, because she had nothing she could believe in. Or just plain believe. Well, we took her and gave her some treatments … I’m a skipper, I don’t know the details … Anyway, she came out of it with what she had when she went in, but more so. Much more. You all felt it—don’t tell me you didn’t. She could make a man doubt his own name.”

Answer 2

And for the sub question, "Why were the scientists brought along?", that was to prime Virginia, as she was the audience for every one of the quacks being undone, thus reinforcing her skepticism. The story analogized it to transporting an atomic bomb in two parts, bringing the pieces together only at the last moment before deployment.