Kapil,
Yes, it is possible to cause a contactor to be held ON due to a single pulse from a sensor. However, you will need some other equipment (other than the sensor pulse and the contactor).
Please list the equipment that you are using. Because you came to a PLC site, I assume that you are using some PLC brand, model, and catalog number. If you list the brand of the PLC, the contactor, and the sensor, and state how long that your sensor input is ON, then we can go from there to answer your question.