Depolarization studies of Mg I, Ca I and Sr I resonance lines involve the excited ¹P state only, the ground state ¹S being unaffected by depolarizing collisions (because calcium has nuclear spin I=0). However, this is not strictly true for Mg I and Sr I but it may be a sufficiently good approximation because their most abundant isotope have indeed I=0; i.e. 90% for Mg I and 93% for Sr I. Concerning the Na I D lines, collisional depolarization occurs both in the ground state (3s ²S_1/2) and in the excited states (3p ²P_1/2 and 3p ²P_3/2). Results have been published for the ground state (see Paper I).

For CaH, accurate ab initio potential energy curves were available (Chambaud & Lévy 1989).

For MgH, the relevant potential energy curves are the third $^2\Sigma^+$ and second $^2\Pi$ states dissociating to the Mg(3s3p ¹P $)+{\rm H}(^2$ S) limit at large internuclear distances (taking into account the ground state $X^2\Sigma^+$ and an intermediate asymptote involving the Mg I atom in a triplet state (3s3p³P). The Gaussian basis set for the H atom comprised the (8s, 4p, 3d) set of Widmark et al. (1990) contracted to [4s, 3p, 2d]. For magnesium, the basis comprised the (14s, 10p) functions of Sadlej & Urban (1991) and the (5d, 4f) functions of Widmark et al. (1991) contracted to [7s, 5p, 4d, 3f]. The total number of contracted Gaussian functions was 86. The potential energy curves were calculated from state average MCSCF wave functions in the $(4\sigma-9\sigma,2\pi-4\pi,1\delta)$ active space.

For SrH, the potential energy curves of interest are the $^2\Sigma^+$ and $^2\Pi$ states dissociating to the Sr(5s5p ¹P $)+{\rm H}(^2$ S) asymptote. This requires calculating five $^2\Sigma^+$ and four $^2\Pi$ states due to the first asymptotes involving the Sr I atom in ¹S, ¹D, ³P and ³D states. The Gaussian basis set for the H atom comprised the (7s, 4p, 3d, 2f) of Kendall et al. (1992) contracted to [5s, 4p]. For the Sr I atom, the basis includes the (11s, 15p, 10d, 6f) of Sadlej & Urban (1991) contracted to [4s, 9p, 4d]. The potential energy curves were calculated from MCSCF wave functions in the $(8\sigma-14\sigma,4\pi-6\pi,2\delta)$ active space.

Adiabatic potential energy curves for NaH have been determined using MRCI wave functions. The basis sets and active space used in these calculations are described in Paper I. The calculations concern the $X^1\Sigma^+$ and a $^3\Sigma^+$ states dissociating to the Na(3s ²S $)+{\rm H}(^2$ S) asymptote and the A $^1\Sigma^+,$ B $^1\Pi,$ b ${^{3}{ \Pi }}$ and c $^3\Sigma^+$ states dissociating to the Na(3p ²P $)+{\rm H}(^2$ S) asymptote.

The results for the three systems are presented in Figs. 1, 2 and 3. The main characteristics of these potential energy curves is the presence of a large well in the ${^{1}{ \Sigma }^{+}}$ states due to the ionic configuration M $^+{\rm H}^-$ (M $^+\equiv {\rm Mg}^+$ ,Sr⁺,Na⁺).

In order to test the basis set and the active space, the minima $R_{\rm e}$ of the attractive X $^1\Sigma^+,$ A $^1\Sigma^+,$ b ${^{3}{ \Pi }}$ states were determined for the well studied NaH system (see Sachs et al. 1975; Pesl et al. 2000; Leininger et al. 2000). A fit of the first vibrational levels gives the harmonic frequency ${\omega}_{\rm e}$ . The vibrational levels were obtained from numerical integration of the radial Schrödinger equation using the Numerov method. The calculated values of these spectroscopic constants are given in Table 1 for comparison with the experimental and theoretical results. Our constants agree well with the experiments and improve some of the available theoretical results.

**Table 1:** Calculated and experimental spectroscopic constants for the X ${^{1}{ \Sigma }^{+}}$ , A ${^{1}{ \Sigma }^{+}}$ and b ${^{3}{ \Pi }}$ states of ²³Na¹H.
State	Reference	$R_{\rm e}$ (a₀)	${\omega}_{\rm e}$ (cm^-1)	$B_{\rm e}$ (cm^-1)	$\alpha_{\rm e}$ (cm^-1)	$D_{\rm e}$ (eV)	$T_{\rm e}$ (cm^-1)
X ${^{1}{ \Sigma }^{+}}$	this work	3.57	1166.7	4.909	0.149	1.89	0
	(Sachs et al. 1975)	3.61	-	-	0.135	1.878	0
	(Meyer & Rosmus 1975)	3.57	1172.3	4.88	0.132	1.92	0
	(Huber & Herzberg 1979)	3.57	1171.4	4.902	-	2.12	0
	(Olson & Liu 1980)	3.558	1171.8	4.927	-	1.922	0
	(Orth et al. 1980)	3.566	1171.4	4.902	0.1386	-	0
	(Pesl et al. 2000)	-	1171.968	4.90327	0.137	-	0

A ${^{1}{ \Sigma }^{+}}$	this work	6.05	313.01	1.7362	-0.0679	1.21	22 310
	(Sachs et al. 1975)	6.19	-	-	-	1.203	22 122
	(Olson & Liu 1980)	5.992	320	1.735	-	1.239	22 568
	(Huber & Herzberg 1979)	6.062	-	-	-	1.41	22 719
	(Orth et al. 1980)	6.0346	317.56	1.712	-0.09152	-	22 713
	(Pesl et al. 2000)	-	319.96	1.70553	-0.0971	-	-

b ${^{3}{ \Pi }}$	this work	4.46	419.88	3.0402	0.239	0.13	31 044
	(Sachs et al. 1975)	4.46	419.39	3.533	0.853	0.109	30 938
	(Olson & Liu 1980)	4.497	430.3	3.09	-	0.133	31 479
	(Huber & Herzberg 1979)	4.195	419	-	-	-	30 940

3 Ab initio potential for the MgH, SrH and NaH systems