  The carrier envelop phase (CEP) of isolated attosecond pulses (IAPs) is
theoretically and experimentally investigated based on the assumption that a
significant contribution originates from the measurable CEP jitter of the
driving laser. By solving the timedependent Schr\"odinger equation, it is
demonstrated that the attosecond CEP jitter of IAPs is minimized when the
driving pulse is near its Fourier limit but with slightly negative chirp.
Although, at present the utilization of the CEP of IAPs has limited
applications, understanding and characterization of the CEP jitter of IAPs is
the first step towards exact control of the electric field of extreme
ultraviolet (XUV) pulses
