Improved collision strengths and line ratios for forbidden [O III]
  far-infrared and optical lines
  Far-infrared and optical [O III] lines are useful temeprature-density
diagnostics of nebular as well as dust obscured astrophysical sources. Fine
structure transitions among the ground state levels 1s^22s^22p^3 \ ^3P_{0,1,2}
give rise to the 52 and 88 micron lines, whereas transitions among the
$^3P_{0,1,2}, ,^1D_2, ^1S_0$ levels yield the well-known optical lines 4363,
4959 and 5007 Angstroms. These lines are excited primarily by electron impact
excitation. But despite their importance in nebular diagnostics collision
strengths for the associated fine structure transitions have not been computed
taking full account of relativistic effects. We present Breit-Pauli R-matrix
calculations for the collision strengths with highly resolved resonance
structures. We find significant differences of up to 20% in the Maxwellian
averaged rate coefficients from previous works. We also tabulate these to lower
temperatures down to 100 K to enable determination of physical conditions in
cold dusty environments such photo-dissociation regions and ultra-luminous
infrared galaxies observed with the Herschel space observatory. We also examine
the effect of improved collision strengths on temperature and density sensitive
line ratios.
