/*
 * physical constants used by Cloudy, taken from
 * Physics Today Aug '96, BG 10
 * Cohen Taylor 1986 Codata, see physics today, Aug '96, p BG11
 */
/*#include "physconst.h"*/

/*********************************************************************
 * first come math constants                                         *
 *********************************************************************/

/* pi */
#define	PI	3.141592654

/* 4\pi */
#define	PI4	12.566371

/* sqrt(pi) */
#define	SQRTPI	1.7724539

/*********************************************************************
 * astronomical constants go here                                    *
 *********************************************************************/

/* solar mass in grams */
#define	SOLAR_MASS	1.9892e33

/* cm in parsec */
#define	PARSEC	3.085678e18

/*********************************************************************
 * fundamental constants go next, eventually rest should be defined  *
 * in terms of these                                                 *
 *********************************************************************/

/* atomic mass unit, grams */
#define	ATOMIC_MASS_UNIT	1.6605402e-24

/* electron mass, grams */
#define ELECTRON_MASS	9.109389754e-28

/* proton mass, grams */
#define PROTON_MASS	1.672623110e-24

/* this is the Boltzmann factor, erg/K */
#define	BOLTZMANN	1.380658e-16

/* speed of light, cm/s */
#define	SPEEDLIGHT	2.99792458e10

/* Planck's constant */
#define	HPLANCK	6.6260755E-27

/*********************************************************************
 * below here should be derived constants                            *
 *********************************************************************/

/* this is the factor that appears in front of boltzmann factor to get
 * LTE level populations for hydrogenic ions.  It is givin in the
 * first parts of section 5 of part 2 of hazy, and is actually
 * ( planck^2 / (2 pi m_e k ) )^3/2, but cannot evaluate powers here,
 * must raise this to 3/2 when used  */
#define HION_LTE_POP	(HPLANCK*HPLANCK/2./PI/BOLTZMANN/ELECTRON_MASS)

/* 1 cm wavenumber in ergs */
#define	ERG1CM	1.98644746e-16

/* ionization potential of real hydrogen atom, in inf mass ryd */
#define	HIONPOT	0.999466508

/* saha is ( h^2/2/pi/m/k )^1.5, is correct constant for free electron */
#define	SAHA	4.141296e-16

/* degrees kelvin per unit wavenumber */
#define	T1CM	1.438769

/* conversion factor from wavenumbers to degrees kelvin - never used */
/*#define	WAVNKELV	1.43883*/

/* 1 infinite mass Rydberg unit in Angrstroms */
#define	RYDLAM	911.26732

/* the temperature of 1 Rydberg */
/* te1ryd is h/k is temp of 1 Rydberg, HOKCGS*nu(912), note that RYDLAM is
 * in Ang but SPEEDLIGHT in cm/s */
#define	TE1RYD	(HPLANCK*SPEEDLIGHT*1e8/RYDLAM/BOLTZMANN) /*1.578866e5*/

/* number of Ryd per wavenumber, from Physics Today '96, BG 10 */
#define	WAVNRYD	9.112670534e-6

/* 1 eV in Kelvin, from Physics Today Aug '96, BG13 */
#define	EVDEGK	1.1604448e4

/* inf mass energy of 1 Ryd in ergs */
#define	EN1RYD	2.179874e-11

/* 1 Ryd (inf mass nucleus) in eV */
#define	EVRYD	13.6056982

/* frequency of one Ryd for infinite mass nuclei */
#define	FR1RYD	3.289841950e15

/* frequency of ionization potential of Hydrogen */
#define	FR1RYDHYD	3.289841950e15

/*2 h nu^2 /c^2 for infinite mass nucleus */
#define	HNU3C2	0.52501302

/* wavelength (A) of ionization potential of Hydrogen */
#define	RYDLAMHYD	911.6