THE INFLUENCE OF NaNa, NaHg ANp NaXe … Bound... · Philips J.Res. 42, 87-101,1987 R1152 THE INFLUENCE OF NaNa, NaHg ANp NaXe MOLECULES ON THE SPECTRUM OF THE HIGH-PRESSURE SODIUM

Philips J. Res. 42, 87-101, 1987 R1152

THE INFLUENCE OF NaNa, NaHg ANp NaXeMOLECULES ON THE SPECTRUM OF THE

HIGH-PRESSURE SODIUM LAMP *)

Abstract

An analysis has been made of the emission spectrum of the high-pressure sodiumlamp. It is shown that the very far wings of the Na D-lines are of (quasi-)molecularorigin, stemming from short range NaNa interaction, as well as from NaHg andNaXe interaction if mercury or xenon is added as a buffer gas. Calculations of theemission spectra incorporating these molecular contributions give good agreementwith measured spectra.

Keywords: discharge lamps, molecular spectra, self-absorption, sodium,spectral line profiles.

by J. J. DE GROOT, J. SCHLEJEN**), J. P. WOERDMAN**)and M. F. M. DE KIEVIET

Philips Lighting Division, 5600 MD Eindhoven, The Netherlands**) Huygens Laboratory, University of Leiden, 2300 RA Leiden, The Netherlands

1. Introduetion

Usually, discharges in sodium vapour are associated with the colour yellow. This isbecause the strongest sodium lines (Na D-lines) have their central wavelengths at589.0 and 589.6 nrn. Well known is the low-pressure sodium lamp 1) with its nearlymonochromatic yellow radiation. For sodium discharges at high pressure") theemitted visible radiation is spread over a much wider range of wavelengths and thecolour of the light emitted may be between that of gold-yellow and white. Thisbroadening of the emitted spectrum is only partly caused by an enhanced linebroadening at higher particle densities. The most important reason is that atsodium densities the absorption of radiation is very strong near the line centre so thatonly photons in the far wings of the Na D-lines can leave the plasma. Thisphenomenon leads to strong self-reversal of the Ddines.

*) Extended version of a contribution to the 4th International Symposium on the Science andTechnology of Light Sources, Karlsruhe, Germany, 1986.

Phlllps Journalof Research Vol. 42 No. 1 1987 87

J. J. de Groot, J. Schlejen, J. P. Woerdman and M. F. M. de Kieviet

Under extreme conditions, viz. combining a large arc radius and a very highsodium vapour pressure, the self-absorption maylead to a complete lack ofyellow radiation and a bluish white spectrum, with daylight colour, as shownin fig. 1. The radiation in the green (with a self-reversal maximum near545 nm) and the red part of the visible spectrum is then dominated by the ex-treme far wings of the Na D-lines. The vibration structure clearly visible inthese spectra indicates that the origin of these far wings in fact is mainly mole-

0.15 -r-----------------"(Wnm-1)

Pi.

t 0.10

0.05

x = 0.334y = 0.305Tc= 5400K

400 500 600 700-- I. (nm)

Fig. 1. Visible spectrum of a special high-pressure sodium discharge, with a complete lack ofyellow radiation, with a colour approximating that of daylight. (x,y) are the chromaticity coordi-nates and Tc is the colour temperature. The K absorption line in the spectrum is due to thepresence of potassium impurities in the discharge.

cular. Also the broad bands at 436.5 and 452 nm, which dominate the violet-blue part of the spectrum, indicate that a description of such spectra in termsof sodium lines is no longer possible. In practical high-pressure sodium (RPS)lamps additional bands may be present in the spectrum when mercury orxenon is present at relatively high pressure.

In this paper an analysis and description of the various spectral features ofRPS lamp spectra will be given.

2. Theory

To understand the spectral features of high-pressure sodium discharges des-cribed above, we have to consider the energy E of two sodium atoms, as afunction of a distance RNaNa, as schematically represented in fig. 2. For a low-pressure sodium discharge we observe the monochromatic yellow

88 Phlllps Journalof Research Vol.42 No. 1 1987

-RNaNa

Infiuence of NaNa, NaHg and NaXe molecules on the spectrum

short range long range

Fig.2. Schematic representation of molecular emission (short range interaction, arrows band b1and atomic emission (long range interaction, arrowa) of a Na + Na quasi-molecule or collisionpair.

radiation of the Na D-lines, generated by an atomic transition to the groundstate as indicated by arrowa. At higher sodium vapour pressures (PNa) there isa wavelength-shift of the radiation emitted, as the energy of the upper level(Eu) is shifted by long-range dipole-dipole interaction of the excited sodiumatom with other sodium atoms in the ground state, whereas the central wave-length is absorbed. At very high sodium vapour pressures the wavelength shiftis dominated by short-range NaNa interaction, leading to a splitting of theatomic levels, and the resulting wavelengths are schematically indicated by thearrows b and b' in fig. 2. In fact such colliding atoms, at short internucleardistance, are quite similar to bound molecules in a spectral sense. We will callthem quasi-molecules or free collision pairs to distinguish them from boundmolecules. The radiation from bound molecules is determined by the samepotential curves and will show (weak) vibrational structure due to the boundstates in the potential wells; the strength of this structure depends on tempera-ture, well depth, and vibrational spacings. However, the radiation frombound molecules is not very important for HP~ lamps, as the bound mole-cules are nearly completey dissociated at the high discharge temperatures 2);the emission spectrum is dominated by that of the quasi-molecules and of theatoms.In the quasi-static approximation of Hedges et al. 3) and Gallagher 4) the

absorption coefficient x for both bound molecules (AB, e.g. Na2) and quasi-,molecules (A +B, e.g. Na + Na) is given by the expression

Phllips Journal uf Research Vol. 42 No. 1 1987 89


1 1t2e2 2 1 [-El(RAB)]

x(v,T) = -4- -2-jgl RAB d [A] [B) exp k '7'() ,1teo me· I dR~ I . J. ' r

(1)

where v is the frequency, T the plasma temperature at radial coordinate r, eothe dielectric constant, e the elementary charge, m the electron mass, c thespeed of light, j the oscillator strength of the transition considered, gl the sta-tistical weight of the lower level, RAB the internuclear separation of the atomsA and B, [A] and [B] are the ground state number densities of the free atomsA and B, and El is the energy of the lower level and k the Boltzmann constant.According to the classical Franck-Condon principle the internuclear distanceand the nuclear kinetic energy do not change during an electronic radiativetransition. Consequently the frequency is given by

(2)

where Eu(RAB) is the energy of the upper level and h is Planek's constant.The right-hand side of eq. (1) describes essentially a Boltzmann distributionof A-B pairs with interaction potential EI(RAB), multiplied by a factor41tR~ dRAB /dv to describe the probability that a transition will occur at a(Condon) point RAB with a frequency between v and v + dv. When the factordv / dRAB becomes zero there will be a singularity in the absorption coefficient.This phenomenon is called a satellite. Such a maximum in the absorptioncoefficient corresponds with an extremum in the potential energy difference,viz. with transitions between parallellying parts of the energy levels, so thatphotons with the same energy (hvs) are generated for a range of internucleardistances around R; as shown schematically in fig. 3. The singularity at thesatellite frequency in the classical quasi-static theory is removed by using thetheory of Szudy and Baylis 5), which gives a semi-classical description of theshape of the satellite.For the calculation of the NaNa absorption coefficient according to eqs (1)

and (2) the contributions of the various optically allowed transitions areadded. The relevant NaNa potential energy curves, associated with the atomicNa 3s- and 3p-Ievels (see fig. 4), have been taken from various literaturesources. We have used experimental data for the singlet potentials: fromKusch and Hessel ") for the Xl:E! and B IIIu potentials, from Zemke et al. 8)for the A l:E~ potential and calculated data from Konowalow et al. 6) for thetriplet potentials. For the upper triplet potentials a shift of about 0.1 eV hasbeen applied to obtain the correct asymptotic frequency for large internucleardistance and to obtain the correct satellite wavelength (see also refs 9 and 10).

90 Phlllps JournnI of Resenrch Vol.42 No. 1 1987

A B

0 ~ K(V)

LRABJ tthVO

EI

b)Vo _V Vs

Influence of NaNa, NaHg and NaXe molecules on the spectrum

Fig. 3. Schematic representation of the occurrence of a satellite in the spectrum. The potentialenergies of the upper level (Eu) and the lower level (El) are given in a) as a function of the inter-nuclear separation of the atoms A and B. The resultant absorption coefficient x(v) is given in b).Apart from the line centre with frequency Vo there is a maximum in the absorption coefficient inthe far wing of the line for the satellite frequency Vs, corresponding with an extremum in thepotential energy difference (Eu - El) at internuclear distance R;

These potential curves are usually given for internuclear distances in the rangefrom 0.2 to 0.8 nm; they are fitted by a polynomial in the reciprocal internuc-lear distance (l/RNaNa) of degree 10. An extrapolation of these potential curves

Fig.4. Lowest-lying Na2 potential energy curves, calculated by Konowalow et al. 6) in dependenceon the internuclear separation RNaNa of the sodium atoms. Dashed line A indicates the Na2 redband system (A 'E~ - X'E;>, B the green Na2 band system (B 'IIu - X'E;) arrow 805 indicatesthe 805 nm satellite of the red band system, 551 the 551.5 nm satellite of the sIT. - 'sE~triplet sys-tem and 882 the 882 nm satellite of the sE; - sE~ triplet system.

E

t

E

(eV)

t

-- RNaNa (nm)

Phillps Journalof Research Vol. 42 No. 1 1987

3s

3p

91


to internuclear distances up to 2 nm is made in such a way that a smooth transi-tion to the long range NaNa interaction 11) occurs. In this way a smooth transi-tion occurs between the quasi-static description of the far wings of the D-linesand the usual description of the D-line broadening by resonance broadeningnear the line centre"). For the oscillator strengths the values of the correlatedatomic transitions have been taken. The expected satellites are indicated infig.4 by arrows with the wavelength observed (551, 805, 882 nm). With suchan analysis various bands in the spectrum of high-pressure sodium dischargescan be identified (fig. 5). There are also bands visible in the ultraviolet andviolet part of the spectrum. An identification of these bands has been madeonly very recently 12). They are satellites arising from transitions from higherlying levels in the sodium (quasi-)molecule to the ground state, associated withthe Na 4s-3s and 3d-3s transitions.

452 551 Na-D436 :

i:805 882

400 500 600 700 800 900

- ).(nm)

Fig. 5. Spectra of an experimental high-pressure sodium discharge at increasing input power andsodium vapour pressure, showing the strong molecular contribution at the extreme self-reversalwidths of the Na D-lines. The origin of the various spectral features is indicated in the figure.

3. Calculated and measured spectra

When the absorption coefficientx(À,r) is known, the spectrum emitted froma plasma in a state of local thermal equilibrium, can be calculated from the


+R [R ~LA = f x(À,r) BA(T) exp - f x(À,r') drJ dr,

-R r

(3)

Infiuence of NaNa, NaHg and NaXe molecules on the spectrum

one-dimensional radiative transfer equation, when the plasma temperaturedistribution T(r) is known 2):

where LA is the spectral radiance, BA(T) the black body (Planck) radiationfunction at wavelength À and temperature T, r the radial coordinate and R theare tube radius. First of all we compare calculated and measured spectra in thevisible and near-infrared wavelength range for a pure sodium discharge; in thesecond and third parts of this section the influence of the buffer gases xenonand mercury will be dealt with.

3.1. Pure sodium discharge

In fig. 6 the spectra that have been measured and calculated are comparedfor a pure sodium discharge *) at a sodium vapour pressure of about 20 kPa.For this calculation a parabolic temperature distribution has been assumedwith an axis temperature TA = 4000 K and a wall temperature Tw = 1500 K,which are typical values for such discharge conditions 2). Apart from the(quasi-)molecular contributions (from the lowest-lying NaNa levels, which infact describe the Na D-line broadening) the recombination radiation and theradiation of the sodium non-resonant lines are included in these calculations 2).In the measured as well as in the calculated spectrum the spectral intensitiesare integrated over I nm intervals. As the measurement has been carried out inan integrating sphere, and not for a line of sight along the diameter of the areas assumed in the calculations, we can only compare the shape of calculatedand measured spectra and not the absolute values. The shapes of the cal-culated and the measured spectrum agree fairly well, although the shape of thesatellite at 551 nm, as calculated with the theory of Szudy and Baylis, isslightly too pronounced. There is also good agreement between the calculatedand measured light-technical data (also given in fig. 6) such as the luminousefficiency V.of the visible radiation, the general colour rendering index Ra andthe correlated colour temperature Tc. At a self-reversal width of the NaD-lines of about 10 nm, which situation is representative of the standard RPSlamp, the satellites at 551 and 805 nm contribute only to a small extent to thespectrum.At much higher values for the sodium vapour pressure, the satellites at 551

and 805 nrn contribute considerably to the spectrum, as shown in fig. 7. This

*) Xenon at a pressure of about 3 kPa is present to make the ignition of the cold lamp possible.This amount of xenon has a negligible influence on the spectrum.

PhllIps Journal of Research Vol. 42 No. 1 1987 93


0.8(Wnm-1)

PI.t 0.6

0.4

Vs=0.564Ra= 23Tc =2050K

measured

400

(Wm-2nm-1sr-1 )

L).

t 600

400

Ra= 28Tc = 2150K

Vs= 0.580

200

500 600 700 800

400 500

calculatedPNa= 20kPaR = 3.8mm

600 700 800- I. (nrn)

Fig. 6. Comparison between measured and calculated spectrum at a sodium vapour pressure of20 kPa and an are radius R = 3.8 mm. P). is the spectral radiant power measured in an integratingsphere, LA the spectral radiance as calculated according to eq. (3), Vs the luminous efficiency of thevisible radiation, R. the general colour rendering index and Tc the correlated colour temperature.

situation is representative of the so-called white RPS lamp. In this case an axistemperature of 3700 K has been assumed in the calculations. Also for suchhigh sodium vapour pressures the model gives a good description of the mea-sured spectrum. At a self-reversal width of the Na D-lines of about 45 nm, amaximum colour rendering index is found, whereas the correlated colour tem-perature approximates that of an incandescent lamp. Because of the strongradiation in the red the luminous efficiency of the visible radiation of such alamp is strongly reduced as compared with the standard RPS lamp. Thiseffect, combined with the stronger radiation in the near-infrared, is the mainreason for the lower luminous efficacy of the 'white' RPS lamp in comparisonwith the standard RPS lamp.

94 Phillps Journalof Research Vol.42 No.l 1987


0.8

(Wnm-1) Vs=0.295 measuredRa=86

Pl. 0.6 Tc =2530K

t0.4

0.2

0400 500 600 700 800

(Wm-2nm-1sr-1 )

L). Vs=0.351 calculated

t 600 Ra=86 PNa= 60kPaTc=2550K R = 3.8mm

400

200

0400 500 600 700 800

-À (nm)

Fig. 7. Comparison between measured and calculated spectrum at a sodium vapour pressure of60 kPa.

3.2. Influence of the buffer gases xenon and mercury

For practical RPS lamps a vapour (Hg) or a gas (Xe) may be added to thesodium discharge to influence its electrical and spectral characteristics 2). Sucha gas or vapour is called a buffer gas. The main influence on the spectrum is anextra broadening of the Na D-lines. This influence can be understood byconsidering the buffer gas atom as the perturber X for the Na atom and bylooking at the potential energy curves of the NaX (quasi-)molecule. When thepotential curves are known the absorption coefficient of the NaX quasi-mole-cule can be calculated from eqs (1) and (2), in a similar way as previously des-cribed for Na-Na. When combining NaX and NaNa the absorption coefficientssimply are added; this approximation is valid for RPS lamp conditions asbinary collisions are dominant and almost all molecules are dissociated.

Phllips Journalof Research Vol. 42 No. 1 1987 95


1(Wm-2nm-1sr-1 )

L).

t 600

400

200

0.5

HPS 150WR = 2.4mmmeasured

o 400

-- I?Na= 13 kPaPXe =330 kPa

----- PNa = 16 kPa

calculated

400 500 600 700-). (nm)

Fig. 8. Influence of the buffer gas xenon on the spectrum of a high-pressure sodium discharge. Themeasurements have been made on a 150W HPS lamp with an are radius R = 2.4 mm. The cal-culations have been made for a parabolic temperature distribution (TA = 4000 K, Tw = 1500 K);data for the sodium and xenon pressures are given in the figure.

In the upper part of fig. 8 the measured spectra of a pure sodium dischargeand a sodium discharge with a relatively high xenon pressure (Pxe) are com-pared for a self-reversal width of the Na D-lines of about 10 nm. In the lowerpart of this figure calculated spectra are compared. For NaXe the potentialcurves have been taken from Jongerius 13). The addition of xenon causes abroad band near 560 nm which is the satellite of the NaXe B2r.+ - X2:r.+ tran-sition. Furthermore, xenon causes an enhancement of the red wing of the NaD-lines, which in fact is due to the NaXe A 2rr - X2:r.+ transition. There isgood agreement between calculations and measurements, although in this casetoo, the calculated satellite is slightly too pronounced.

Fig.9 shows, in a similar way, the effects ofthe buffer gas mercury. For thepresent calculations the NaHg potential curves of Hüwel et a1.14) have beenmodified as discussed in ref. 15. The main effect of mercury is an asymmetriebroadening to the red of the Na D-lines with a band at 671 nm, which may be



Fig. 9. Influence of the buffer gas mercury on the spectrum of a high-pressure sodium discharge.

considered as the satellite of the NaHg B2r, - X2r, transition. The measuredstructure near this maximum cannot be explained with the quasi-static theory.In the UV-blue part of the spectrum some bands are visible with peaks at 453and 470 nm, ascribed to NaHg (quasi-)molecules. So far these bands have notbeen identified. Experimental data indicate that they arise from a transition tothe NaHg ground state. For the present calculations the absorption coefficientof these bands has been taken proportional to the sodium and mercury groundstate densities, while the proportionality constant and the wavelength depen-dence were taken from absorption measurements.

3.3.Colour, luminous efficiency and luminous efficacy

The changes in the spectrum due to the addition of a buffer gas will have aninfluence on the colour of the light emitted as well as on the luminous effi-ciency of the visible radiation and the related luminous efficacy of the lamp 2).The colour of the light is usually characterized by the chromaticity coordinatesor the colour point in the colour triangle. Fig.IO shows the effects ofthe xenon

Li.I 600I400

200

measuredHPS 150WR = 2.4mm

500 600 700

PNa~ 15kPaPHg~ 225kPa

PNa~ 16kPacalculated

400 500 600 700-). (nm)

Philip. Journol of Research Vol. 42 No. 1 1987 97


0040

measuredcalculated;\1.=10nm

y

t 0045

0.35 L- _.__ ...L_ ~

0.50 0.55 0.60 0.65x

Fig. ID. Influence of the buffer gases xenon and mercury on the colour point in the colour triangle.Data apply for a self-reversal width of the sodium D-lines.ó.À '" 10 nm. Data for are radius, par-tial pressures and plasma temperature are given in table 1. Measured data have been taken fromref.2.

TABLE I

Influence of the buffer gases xenon and mercury on the luminousefficiency V. of the visible radiation. Data apply for a self-reversal width of

the D-lines ~À :::=: 10 nm. Calculations have been made for a constantplasma temperature distribution.

R = 2.4 mm ~À = 10 nm

PNB pXe PHg Vs V.(kPa) - - calcPNB PNB meas19 - - 0.63 0.5815 25 - 0.60 0.5713 - 7 0.55 0.5610 25 7 0.57 0.56

TA = 4000 K Tw = 1500 K

or mercury addition on the colour point of an RPS discharge. Calculatedvalues are given for a constant self-reversal width (~À) ofthe Na D-lines and aconstant plasma temperature distribution. The calculated shift in the colourpoint agrees reasonably well with the measured shift. The addition of xenon toa sodium discharge causes the colour point to shift toward the yellow regionof the spectral locus in the colour triangle. This can be understood from theinfluence xenon has on the spectrum: the extra radiation in the green (560 nm



band) and in the red (long-wavelength wing of the Na D-lines) has the sameeffect on the colour point as extra yellow radiation. The addition of mercurycauses the colour point to shift towards the red region of the colour triangleas the main effect of mercury is an enhanced radiation in the red part of thespectrum. A limited shift towards the red is desirable in order to obtain acolour point lying nearer to the black body locus (BBL) than in the case of apure sodium discharge.

Fig. 10 also shows the effect of a combination of two buffer gases (Hg andXe) on the colour point of an HPS discharge. When xenon is added to anNa + Hg discharge there is a (small) colour shift toward the yellow-green spec-tral region instead of towards the yellow as observed when xenon is added to apure sodium discharge. This effect of the combination of the buffer gases Xeand Hg can be understood from the characteristic NaXe and NaHg spectra:part of the NaXe emission spectrum in the red wing of the Na D-lines will beabsorbed by the NaHg quasi-molecules, while the NaXe contribution in theblue wing of the D-lines remains undisturbed. The effects of the various buffergases on the emitted spectrum are not additive (as is the case for the absorp-tion coefficient) because of the self-absorption; therefore a simple linearcombination of the effects of the separate buffer gases does not describe theactual effects very well. The present model, based on a full calculation of theemitted spectrum, describes the measured shift in colour point reasonablywell, also for a combination of various buffer gases.The influence of the addition of a buffer gas on the luminous efficiency of

the visible radiation is shown in table I.Calculated values are given for a con-stant self-reversal width (~À) of the Na D-lines and a constant plasma tempe-rature distribution. The addition of xenon to a pure sodium discharge onlyslightly reduces the luminous efficiency. The addition of mercury has a farmore negative effect on the luminous efficiency, as the NaHg radiation is gen-erated mainly in the red, where the spectralluminous efficiency for the humaneye is relatively low. The measured luminous efficiency values in table I showthese effects of xenon and mercury to be less pronounced, because of actualdifferences in plasma temperature, impurities etc., and because of radiationfrom the buffer gas, which effects are not taken into account in the calcula-tions. When xenon is added to an Na + Hg discharge the luminous efficiency isnot reduced further, as one would expect for a simple linear combination ofthe effects of the buffer gases separately. This again is due to the fact that theeffects of the buffer gases on the emitted spectrum are not additive, because ofthe influence of self-absorption.

The calculations in table I further show that at increasing buffer gas pres-sure a lower sodium vapour pressure is needed to get the same self-reversal

Phllips Journalof Research Vol.42 No. 1 1987 99


width of the Na D-lines. This is because of the extra line broadening. Con-sequently the radiant power of the non-resonant Na lines in the infrared willbe lower (when the plasma temperature is about the same). This has a favour-able effect on the useful visible radiation, at the cost of the useless infraredradiation, of such a light source. This is one of the major reasons why animprovement of 10 to 150/0in luminous efficacy (luminous flux divided byinput power) is obtained when a high xenon pressure is added to a standardNa + Hg discharge lamp").

4. Conclusions

NaNa, NaXe and NaHg (quasi-)molecules significantly affect the spectrumand consequently the light-technical data of high-pressure sodium lamps.With our model, these effects are described rather well, as we have shown witha few examples.

100 Phillps Journalof Research Vol.42 No. 1 1987

REFERENCES1) J. W. Denneman, LE.E. Proc. Pt.A 128, 397 (1981).2) J. J. de Groot and J. A. J. M. van Vliet, The high-pressure sodium lamp, Philips

Technical Library, KIuwer Technische Boeken B.V., Deventer, 1986.3) R. E. M. Hedges, D. L. Drummond and A. GaIIagher, Phys, Rev. A 6, 1519 (1972).4) A. GaIIagher, Metal vapor excimers, Ch, 5 in Topics in Applied Physics, ed. C. K. Rhodes,

Springer, New-York 30, 135 (1979).6) J. Szudy and W. E. BayIis, 1. Quant. Spectrosc. Radiat. Transfer 15, 641 (1975).6) D. D. Konowalow, M. E. Rosenkrantz and M. L. Olson, J. Chern. Phys. 72, 2612

(1980).7) P. Kusch and M. M. Hessel, J. Chem. Phys, 68,2591 (1978).8) W. T. Zemke, K. K. Verma, T. Vu and W. C. StwaIIey, J. Molec. Spectrosc. 85, 150

(1981).9) J. P. Wo er.drn a n and J. J. de Groot, Chem. Phys, Lett. 80, 220 (1981).10) J. P. Woerdman and J. J. de Groot, in Metal Bonding and Interactions in High Tempera-

ture Systems, eds Gole and StwaIIey, ACS Symposium Series, no. 179Washington D.C.,33-41, 1982.

") B. Bussery and M. Aubert-Frécon, J. Chem. Phys. 82, 3224 (1985).12) J. Schlejen, J. Mooibroek, J. Korving, J. P. Woerdman and J. 1. de Groot, Chern.

Phys. Lett. 128, 489 (1986).13) M. J. Jongerius, 38th Gaseous Electronics Conf., Monterey, 1985.14) L. Hüwel, J. Maier and H. Pauly, J. Chem. Phys. 76, 4961 (1982).16) J. P. Woerdman, J. Schlejen, J. Korving, M. C. van Hemert, J. J. de Groot and

R. P. M. van Hal, J. Phys. B: Atom. Mol. Phys. 18,4205 (1985).


AuthorsJ. J. de Groot; Ir. degree (Physics), Technical University Eindhoven, 1970; Ph.D., TechnicalUniversity Eindhoven, 1974; Central Development laboratory of the Philips Ligthing Division,Eindhoven, 1970- . His thesis work was on high-pressure sodium and mercury/tin iodide arcs.He is presently involved in the research and development of low-pressure sodium lamps. He andJ. A. van Vliet are the authors of a book "The high-pressure sodium lamp", which appeared inthe Philips Technical Library, 1986.

J. Schlejen; Drs degree (Experimental Physics), University Of Leiden, The Netherlands, 1983;Huygens Laboratory, Leiden, 1983- . He has been working in the field of far-infrared spectro-scopy at the Kamerlingh Onnes Laboratory, Leiden. He is presently preparing his Ph.D. thesis onspectroscopy of Na-Na and Na-Hg vapours at the Huygens Laboratory, Leiden.

J. P. Woerdman; Drs degree (Experirnental Physics), University of Amsterdam, TheNetherlands, 1968; Ph.D., University of Amsterdam, 1971; Philips Research Laboratories, Eind-hoven, 1968-1983; Professor of Experimental Physics, University of Leiden, 1983- . In 1975 hestayed at Bell Laboratories in Murray Hill, U.S.A., for one year. His current resposabilities are inthe fields of Molecular Physics and Quantum Electronics.

M. F. M. de Kieviet is completing his studies for the Drs degree (Experimental Physics andChemistry) at the University of Leiden, The Netherlands. From 1983-1985 he cooperated in a re-search program on the far wing broadening of the Na-D line due to Na, Hg and Xe. In 1985 heparticipated in related work at the Central Development Laboratory of the Philips LightingDivision. In 1986 he spent a year in the surface science group at the University of Genoa, Italy.

Phlllps Journalof Research Vol. 42 No. 1 1981 101

Documents

THE INFLUENCE OF NaNa, NaHg ANp NaXe … Bound... · Philips J.Res. 42, 87-101,1987 R1152 THE INFLUENCE OF NaNa, NaHg ANp NaXe MOLECULES ON THE SPECTRUM OF THE HIGH-PRESSURE SODIUM