Observing bands which I shouldn't be!

I performed the iodine spectrum experiment to observe vibronic transitions. I heated the iodine crystals to produce vapors (at a little above room temperature) and observed absorption spectrum with a diffraction grating and a spectrometer. But I am getting some quirky results as indicated following.


1. In [Ref 1](https://aapt.scitation.org/doi/10.1119/1.15914) and [Ref 2](https://www.semanticscholar.org/paper/The-Iodine-Spectrum-Zielinski-Long/2dbfbab4ad77eea819afbed8800fe7a5f26da86e), it is stated that near room temperatures, $I\_2$ 
is in the ground electronic state and in the lowest vibrational state too ($X, 
v''=0$ state), so transitions are observed only from thsat state.
2. [Ref 2](https://www.semanticscholar.org/paper/The-Iodine-Spectrum-Zielinski-Long/2dbfbab4ad77eea819afbed8800fe7a5f26da86e), [Ref 3](http://homepages.gac.edu/~anienow/CHE-372/Labs/I2lab.pdf), [Ref 4](https://pubs.acs.org/doi/abs/10.1021/ed039p626) and [Ref 5](http://websites.uwlax.edu/aloh/pdf_files/chm313_pdf/Manual_current/chm313_Expt6_I2.pdf) state that from $X, v''=0$ state, Franck-Condon principle tells that transitions can be observed only to $B, v'$ states with $v'$ ranging around $20-50$, and they also cite the standard values of energies corresponding to particular $v'$ values so as to numerate the observed bands accordingly.


Now, at near room temperatures, I after numerating my bands, observed that I was seeing dark bands for $v'=0$ onwards! (I after assigning the standard band, numerated the lower energy bands backwards.) So, one of the above points have to be false!


**Questions:** Please tell what can possibly go wrong? If I'm getting some contributions from $X, v''>0$ states, how to identify them (since [Ref 4](https://pubs.acs.org/doi/abs/10.1021/ed039p626) clearly states that the bands with transitions from $x, v''>0$ states "should not be included in this numeration" in for calculating the parameters from Birge-Sponer plot)?


