Gaseous system: Meaning of this integral eq.

jam_27

What is the physical or statistical meaning of the following integral

[tex]\int^{a}_{o} g(\vartheta) d(\vartheta)[/tex] = [tex]\int^{\infty}_{a} g(\vartheta) d(\vartheta)[/tex]

where [tex]g(\vartheta)[/tex] is a Gaussian in [tex]\vartheta[/tex] describing the transition frequency fluctuation in a gaseous system (assume two-level and inhomogeneous) .

[tex]\vartheta = \omega_{0} -\omega[/tex], where [tex]\omega_{0}[/tex] is the peak frequency and [tex]\omega[/tex] the running frequency.

I understand that the integral finds a point [tex]\vartheta = a[/tex] for which the area under the curve (the Gaussian) between 0 to a and a to [tex]\infty[/tex] are equal.

But is there a statistical meaning to this integral? Does it find something like the most-probable value [tex]\vartheta = a[/tex]? But the most probable value should be [tex]\vartheta = 0[/tex] in my understanding! So what does the point [tex]\vartheta = a[/tex] tell us?

I will be grateful if somebody can explain this and/or direct me to a reference.

Cheers

Jamy