Fig. 5: Molecule size maps of PAH molecules in gaseous form based on LIF anisotropy lifetime maps from the 50-Gfps and 25-Gfps imaging results.

a–h Results of 50-Gfps imaging. (i–p), Results of 25-Gfps imaging. a, i 2D maps of the volumes of PAH molecules. e, m 2D maps of the sizes of PAH molecules. b, f, j, and n Magnified views of molecule volume and size maps in the center regions of the flame, enclosed by dashed boxes in (a), (e), (i), and (m). The colormaps are rescaled. Scale bars in (a), (e), (i), and (m): 2 mm. Scale bars in (b), (f), (j), and (n): 0.5 mm. c, g Average PAH volumes along the \(y\)-direction and at two selected positions [v1 and v2 labeled in (a, e)]. d, h Average PAH volumes along the \(x\)-direction and at two selected positions [h1 and h2 labeled in (a, e)]. k, o Average PAH sizes along the \(y\)-direction and at two selected positions [v1 and v2 labeled in (i, m)]. l, p Average PAH sizes along the \(x\)-direction and at two selected positions [h1 and h2 labeled in (i) and (m)]. In (c, d) the directions of PAH molecule growth are marked by orange arrows. In (c–p) the red solid lines are for the spatially averaged values, and the black short-dashed and long-dashed lines are for two selected positions. q, s Contour plots of molecule volume growth in space by taking spatial gradients of (a) and (i). r, t Contour plots of molecule size growth in space by taking spatial gradients of (e) and (m). The lengths and directions of the black arrows in (q–t) represent the amplitudes and directions of spatial growth. Scale bars in (q–t): 0.25 mm.