  A new technique for obtaining switched wave packets using spectrally
truncated chirped laser pulses is demonstrated experimentally and numerically
by one-dimensional alignment of both linear and asymmetric top molecules. Using
a simple long-pass transmission filter, a pulse with a slow turn on and a rapid
turn off is produced. The degree of alignment, characterized by
$\langle\cos^2\theta_\text{2D}\rangle$ rises along with the pulse intensity and
reaches a maximum at the peak of the pulse. After truncation
$\langle\cos^2\theta_\text{2D}\rangle$ drops sharply but exhibits pronounced
half and full revivals. The experimental alignment dynamics trace agrees very
well with a numerically calculated trace based on solution of the
time-dependent Schr\"odinger equation. However, the extended periods of
field-free alignment of asymmetric tops following pulse truncation reported
previously is not reproduced in our work.
