Nozzle Assemblies and methods of use for producing a liquid jet are disclosed that may be permit adjustable time delays between mixing of fluids and observation of reactions. An example nozzle assembly includes: a housing having an inlet and an outlet and a first channel defined therebetween, where the housing includes a gas focusing aperture defining the housing outlet; an intermediate tube disposed within the first channel of the housing, where the intermediate tube has an inlet and an outlet and defines a second channel therebetween; and a central tube disposed within the second channel of the intermediate tube, where the central tube has an inlet and an outlet and defines a third channel therebetween, where the central tube outlet is longitudinally spaced apart from the intermediate tube outlet such that the intermediate tube outlet is disposed between the central tube outlet and the gas focusing aperture's inlet.