  In this paper we study the properties of the optical spectra of Type 1 active
galactic nuclei (AGNs) by using the unobscured hard X-ray emission as a
diagnostic. We develop the `Correlation Spectrum Technique' (CST) and use this
to show the strength of correlation between the hard X-ray luminosity and each
wavelength of the optical spectrum. This shows that for Broad Line Seyfert 1s
all the strong emission lines (broad component of H\alpha and H\beta, [NeIII]
\lambda\lambda 3869/3967, [OI] \lambda\lambda 6300/6364, [OII] \lambda\lambda
3726/3729, [OIII] \lambda\lambda 4959/5007) and the optical underlying
continuum all strongly correlate with the hard X-ray emission. But the NLS1s
appear to be somewhat different. Among the various Balmer line components and
the broadband SED components, the best correlation exists between the hard
X-ray component and broad component (BC) of the Balmer lines, which supports
the view that broad line region (BLR) has the closest link with the AGN's
compact X-ray emission. The equivalent widths of Balmer line IC and BC are
found to correlate with L$_{2-10keV}$, $\kappa_{2-10keV}^{-1} =
L_{bol}/L_{2-10keV}$, Balmer line FWHM and black hole mass. There is a
non-linear dependence of the Balmer line IC and BC luminosities with
L$_{2-10keV}$ and L$_{5100}$, which suggests that a second-order factor such as
the ILR and BLR covering factors affect the Balmer line component luminosities.
The Balmer decrement is found to decrease from ~5 in the line core to ~2 in the
extended wings, with mean decrements of 2.1 in BLR and 4.8 in ILR. This
suggests different physical conditions in these regions. The [OIII] line is
composed of a narrow core together with a blue-shifted component with average
outflow velocity of $130^{+230}_{-80} km s^{-1}$. The total luminosity of
[OIII] \lambda 5007 well correlates with the hard X-ray luminosity.

High Energy Astrophysical Phenomena;Cosmology and Nongalactic Astrophysics