I did a TDDFT calculation using B3LYP functional and ground state optimized structure in NWCHEM. The TDDFT portion of the output is the following:
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Root 1 singlet a 0.124505160 a.u. 3.3880 eV
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Transition Moments X -0.67477 Y -0.16090 Z -0.00926
Transition Moments XX -3.72551 XY 0.33692 XZ 0.29211
Transition Moments YY 1.03517 YZ -0.47531 ZZ 0.23052
Dipole Oscillator Strength 0.0399490230
Electric Quadrupole 0.0000000711
Magnetic Dipole 0.0000000066
Total Oscillator Strength 0.0399491007
Occ. 118 a --- Virt. 119 a -0.98715 X
Occ. 118 a --- Virt. 120 a 0.09973 X
Occ. 118 a --- Virt. 121 a 0.09163 X
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Root 2 singlet a 0.137354088 a.u. 3.7376 eV
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Transition Moments X -0.76724 Y -0.18948 Z -0.00938
Transition Moments XX -0.14340 XY 0.42578 XZ 0.40121
Transition Moments YY -3.78588 YZ -0.70760 ZZ 0.22932
Dipole Oscillator Strength 0.0571987020
Electric Quadrupole 0.0000000795
Magnetic Dipole 0.0000001012
Total Oscillator Strength 0.0571988827
Occ. 117 a --- Virt. 119 a 0.06721 X
Occ. 118 a --- Virt. 119 a -0.08427 X
Occ. 118 a --- Virt. 120 a -0.97488 X
Occ. 118 a --- Virt. 121 a 0.16187 X
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Root 3 singlet a 0.146507598 a.u. 3.9867 eV
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Transition Moments X -1.29377 Y -0.16851 Z -0.08944
Transition Moments XX -3.80151 XY -0.41951 XZ 0.03490
Transition Moments YY -2.01247 YZ -0.69574 ZZ 0.28749
Dipole Oscillator Strength 0.1670425890
Electric Quadrupole 0.0000000814
Magnetic Dipole 0.0000000321
Total Oscillator Strength 0.1670427025
Occ. 117 a --- Virt. 119 a 0.46050 X
Occ. 118 a --- Virt. 119 a -0.10314 X
Occ. 118 a --- Virt. 120 a -0.09062 X
Occ. 118 a --- Virt. 121 a -0.85863 X
Occ. 118 a --- Virt. 122 a -0.06947 X
Occ. 118 a --- Virt. 124 a -0.08528 X
Occ. 118 a --- Virt. 126 a -0.06728 X
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Root 4 singlet a 0.148144715 a.u. 4.0312 eV
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Transition Moments X 0.71163 Y 0.25036 Z -0.00906
Transition Moments XX -0.55692 XY -1.07219 XZ -0.77683
Transition Moments YY 3.20588 YZ 0.77510 ZZ -0.25256
Dipole Oscillator Strength 0.0562132776
Electric Quadrupole 0.0000001164
Magnetic Dipole 0.0000002325
Total Oscillator Strength 0.0562136265
Occ. 117 a --- Virt. 119 a 0.87602 X
Occ. 118 a --- Virt. 120 a 0.12925 X
Occ. 118 a --- Virt. 121 a 0.44044 X
Occ. 118 a --- Virt. 122 a 0.08258 X
Occ. 118 a --- Virt. 124 a 0.07882 X
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Root 5 singlet a 0.154029225 a.u. 4.1914 eV
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Transition Moments X 1.06235 Y -1.10313 Z -0.02692
Transition Moments XX 12.18774 XY 1.28925 XZ 0.69277
Transition Moments YY-12.48775 YZ 0.01961 ZZ -0.04038
Dipole Oscillator Strength 0.2409235301
Electric Quadrupole 0.0000030040
Magnetic Dipole 0.0000000646
Total Oscillator Strength 0.2409265987
Occ. 116 a --- Virt. 119 a 0.08704 X
Occ. 116 a --- Virt. 121 a 0.05730 X
Occ. 116 a --- Virt. 126 a -0.06016 X
Occ. 117 a --- Virt. 119 a 0.05311 X
Occ. 117 a --- Virt. 121 a -0.11048 X
Occ. 118 a --- Virt. 121 a 0.09638 X
Occ. 118 a --- Virt. 122 a -0.96960 X
Occ. 118 a --- Virt. 126 a 0.05824 X
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Root 6 singlet a 0.160861901 a.u. 4.3773 eV
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Transition Moments X 0.03641 Y -0.03873 Z 0.00124
Transition Moments XX 4.34168 XY 0.32728 XZ 0.54758
Transition Moments YY -3.07040 YZ -0.31294 ZZ 0.02520
Dipole Oscillator Strength 0.0003032394
Electric Quadrupole 0.0000003184
Magnetic Dipole 0.0000001208
Total Oscillator Strength 0.0003036786
Occ. 117 a --- Virt. 120 a -0.96655 X
Occ. 117 a --- Virt. 122 a 0.07250 X
Occ. 118 a --- Virt. 120 a 0.05042 X
Occ. 118 a --- Virt. 123 a 0.17409 X
Occ. 118 a --- Virt. 124 a -0.10164 X
Occ. 118 a --- Virt. 126 a 0.05475 X
For my molecule experimental absorbance is at 321 nm or 3.8624 eV.
My question is that from my output which root should I compare with the experimental value?
Do I need to consider oscillator strength or I should take the root 1 value?