We perform a phenomenological analysis of the decays

\bar{B} \to D^{**} π

, where

D^{**}

is a

P

-wave excited meson with total angular momentum

j = \frac{1}{2}

\frac{3}{2}

for the light cloud, recently measured by the Belle Collaboration in the modes

{\bar{B}}^{0} \to D^{** +} π^{-}

(Class I) and

B^{-} \to D^{** 0} π^{-}

(Class III). Making the reasonable assumption of naive factorization, that we test in

B \to D (D^{*}) π

decays, Class I decays allow to extract the Isgur-Wise form factors

τ_{1 / 2} (w)

τ_{3 / 2} (w)

w ≅ w_{\max}

(

q^{2} ≅ 0

). We obtain

τ_{1 / 2} (w_{\max}) < 0.20

τ_{3 / 2} (w_{\max}) = 0.31 \pm 0.12

. We discuss the question of the

w

dependence of these IW functions. We find agreement with the Bakamjian-Thomas quark model of form factors and, extrapolating at

w = 1

, with Bjorken and Uraltsev sum rules. We discuss also Class III decays, where the

D^{** 0}

(j = \frac{1}{2})

emission diagram contributes. We extract the corresponding

f_{D_{1 / 2}}

decay constant, that is in agreement with theoretical estimates at finite mass. Finally, we must warn that

1 / m_{Q}

corrections could be large and upset the results of the present stage of this analysis. On the other hand, we confront present data on the semileptonic rate of

B

mesons to excited states with theoretical expectations.

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