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At the epoch of reionization, when the high-redshift inter-galactic medium (IGM) is being enriched with metals, the 63.2 micron fine structure line of OI is pumped by the ~ 1300 AA soft UV background and introduces a spectral distortion in the Cosmic Microwave Background (CMB). Here we use a toy model for the spatial distribution of neutral oxygen, assuming metal bubbles surround dark matter halos, and compute the fluctuations of this distortion, and the angular power spectrum it imprints on the CMB. We discuss the dependence of the power spectrum on the velocity of the winds polluting the IGM with metals, the minimum mass of the halos producing these winds, and on the cosmic epoch when the OI pumping occurs. We find that, although the clustering signal of the CMB distortion is weak \delta y_{rms} ~ 10^{-7} (roughly corresponding to a temperature anisotropy of few nK), it may be reachable in deep integrations with high-sensitivity infrared detectors. Even without a detection, these instruments should be able to useful constraints on the heavy element enrichment history of the IGM., Comment: Accepted for publication to ApJ

We consider the pumping of the 63.2 mm fine-structure line of neutral Oi in the high-redshift intergalacticmedium (IGM), in analogy with the Wouthuysen-Field effect for the 21 cm line of cosmic H i. We show that the soft UV background at ! 1300 can affect the population levels, and if a significant fraction of the IGM volume is filled

We study the constraints that future multifrequency Cosmic Microwave Background (CMB) experiments will be able to set on the metal enrichment history of the Inter Galactic Medium at the epoch of reionisation. We forecast the signal to noise ratio for the detection of the signal introduced in the CMB by resonant scattering off metals at the end of the Dark Ages. We take into account systematics associated to inter-channel calibration, PSF reconstruction errors and innacurate foreground removal. We develop an algorithm to optimally extract the signal generated by metals during reionisation and to remove accurately the contamination due to the thermal Sunyaev-Zel'dovich effect. Although demanding levels of foreground characterisation and control of systematics are required, they are very distinct from those encountered in HI-21cm studies and CMB polarization, and this fact encourages the study of resonant scattering off metals as an alternative way of conducting tomography of the reionisation epoch. An ACT-like experiment with optimistic assumtions on systematic effects, and looking at clean regions of the sky, can detect changes of 3%-12% (95% c.l.) of the OIII abundance (with respect its solar value) in the redshift range $z\in$ [12,22], for reionization redshift $z_{\rm re}>10$. However, for $z_{\rm re}, 10 pages, 2 figures, submitted to Astrophysical Journal. Comments are welcome