Particle System in Cocos2dx 2.1.5

I set a Duration for a emitter ,but when the emitter’s duration time up, emitter stop emit,and all the particles disappear at the same time.

I find that the emitter was deleted ,but there are still particles exist.Isn’t it deleted when all the particles’life end ? Why does this happened?

I just need emitter stop emit and let the rest of particles move.my code like this:
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CCParticleSystem *emitter = CCParticleSystemQuad::create(“newrecord_particle.plist”);
emitter~~>setPosition);
emitter~~>retain();
emitter~~>setAutoRemoveOnFinish;
this~~>addChild(emitter,4);
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