A Summary of

Hydrogen Spectroscopy

Jochen Walz

Institut für Physik, Johannes Gutenberg-Universität Mainz

Helmholtz-Institut Mainz

Theodor W. Hänsch,

Arthur L. Schawlow, and

Geoge W. Series:

“The Spectrum of Atomic Hydrogen,”

Sci. Am. March 1979, p. 72–86

T. W. Hijmans et al., J. Opt. Soc. Am. B 6 (1989) 2235–43

1 S – 2 P and 1 S – 2 S Transitions

2 P: τ ' 1.6 ns → ∼ 100 MHz natural linewidthstrong transition, λ = 121.6 nm (Lyman-α)

use: laser-cooling

2 S: τ ' 120 ms → ∼ 1 Hz natural linewidthtwo-photon transition, each photon at λ = 243 nm

linear Doppler-effect cancels,

if photons come from opposite directions

ν/ν0 = 1 + ~k · ~v − v2/2c2 +O(v4/c4)

use: test of QED, ground-state Lamb-shift, rD/rp,

Rydberg constant (combined with other transitions),

drift of fundamental constants, . . .

2 S – 2 P mixing: electric field (few V / cm)

→ can detect 2 S excitation by fluorescence at Lyman-alpha

1 S –2 P

Lyman-α spectroscopy

Four-wave mixing in mercury vapour

LN2 trap

pumpturbo

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alignmentµ30 m pinhole

CW Ti:Sapph.

LBO

798 nm

SHG

BBO

SHG

rotation

DM

DM

polarisation

Single modeAr−ion laser 257 nm

(900 mW)

399 nm(920 mW)Ar−ion laser

CW Dye−laser

545 nm (1.7 W)

514 nm

He

f=20 cm

220 oCmercury heatpipe

1.014 umAPD

2MgF L − filtersα

vacuum setup

PM

121.56 nm

counterphoton

DM6 P

6 S

12 P

1

7 S1

6 P3

1

257 nm

399 nm

545 nm

121.6 nm

Hg

1014 nm

1,3

Hg

AC

ACLyman-α generation

laser system

K. S. Eikema et al. PRL 83 (1999) 3828, M. Scheid at al. Opt. Lett. 32 (2007) 955

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α

LN2trap

LN2trap

turbopump

turbopump

turbopump

turbo−pump

He

LN2 trap

15 mmcool

ing

+ 15 cm

wavelengthsfundamental

heated

mercuryheatpipe

cooledHg

heated

MgF2

argon

MgF2 lenses

pinhole0.5 mm

APDDM

1014 nm filter

dissociator

collimation 1:250

80K

LN2

0.8 mm

PM

vacuum

photon counting

Lyman−filters

PM

Lyman −α

H2

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Lyman-α spectrum at almost natural linewidth

1s2S

1/22p

2P

3/2

Fg

= 0

Fg

= 1

0 1000 2000 3000 4000

detuning at 121,56 nm [MHz]

100

300

500

700

VUV fluorescence[counts/0,5 s]

Fg=1

Fg=0

1420.4 MHz

23.7 MHzF

e=2

Fe=1

12S

1/2

22P,S

1/2

22P

3/2

1 25 λ = 121.56 nm

Γ2p

= 99.7 MHz

FWHM = 119± 2 MHzfür Fg = 1

FWHM = 120± 3 MHzfür Fg = 0

the natural linewidth isΓ = 99,7 MHz

K. S. E. Eikema, J. W., and T. W. Hänsch: PRL 86 (2001) 56798

1 S –2 S

two-photon spectroscopy

Early 1 S – 2 S two-photon spectroscopy

pulsed dye laser (pressure-tuned) (at λ = 486 nm → frequency-doubling)comparison with Balmer-β

T. W. Hänsch, S. A. Lee, R. Wallenstein, and C. Wieman, Phys. Rev. Lett. 34 (1975) 307

continuous dye laser, 130Te2 wavelength reference

J. R. M. Barr et al., Phys. Rev. Lett. 56 (1986) 580

D. H. McIntyre et al., Phys. Rev. A 39 (1989) 4591 7× 10−10

Hydrogen atomic beam apparatus at MPQ Garching

T. W. Hänsch, Nobel Lecture 2005

T. W. Hänsch, Nobel Lecture 2005

Transportable infrared frequency reference

CH4-stabilized HeNe-laser at 3.392 µm (Chebotaev-group, Novosibirsk)

fr = 88 376 181 599.67(15) kHz, 1.8× 10−12

7-th harmonic of fr:

618.633 THz

1 S – 2 S transition frequency:

f0 = 2 466.061 413 187 018 (11) THz

frequency of the blue laser (λ = 486 nm), f0/4:

616.515 THz

→ can use fr as a frequency reference, but there is a2.1 THz frequency gap in the blue

T. Andreae et al., Phys. Rev. Lett. 69 (1992) 1923 2.8× 10−11

Thomas Udem

Habilitationsschrift

2004

Optical frequency interval divider

H. R. Telle et al., Opt. Lett. 15 (1990) 532

Optical frequency interval divider chain

Th. Udem et al., Phys. Rev. Lett. 79 (1997) 2646, 3.4× 10−13

M. Niering et al., Phys. Rev. Lett. 84 (2000) 5496 1.8× 10−14

measurement with

frequency-comb

referenced to

Cs atomic clock

M. Fischer et al., Phys. Rev. Lett. 92 (2004) 230802 1.4× 10−14

measurement with

self-referenced

frequency-comb,

referenced to

Cs atomic clock

1 S –2 S frequency measurement referenced to national standard Cs clock

A. Matveev et al., Phys. Rev. Lett. 110 (2013) 230801, 4.5× 10−15

A. Matveev et al., Phys. Rev. Lett. 110 (2013) 230801, 4.5× 10−15

2 466 061 413 187 018 (11) Hz

A. Matveev et al., Phys. Rev. Lett. 110 (2013) 230801, 4.5× 10−15

spectroscopy with

trapped hydrogen atoms

Spectroscopy with trapped hydrogen atoms

Amsterdam: J. T. M. Walraven et al. pulsed Lyman-α laser cooling

MIT: D. Kleppner et al. 1 S – 2 S spectroscopy

Motivation for both experiments: Bose-Einstein condensation

Relevance to our field: use few antihydrogen atoms efficiently

O. J. Luiten et al., Appl. Phys. B 59 (1994) 311

Pulsed Lyman-α laser cooling at Amsterdam

I. D. Setija et al., “Optical cooling of atomic hydrogen in a magnetic trap,” Phys. Rev. Lett. 70 (1993) 2257

Claudio Lenz Cesar, PhD thesis (MIT), 1995

1 S – 2 S two-photon spectroscopy at MIT

Claudio L. Cesar et al., “Two-Photon Spectroscopy of Trapped Atomic Hydrogen,” Phys. Rev. Lett. 77 (1996) 255

diagnostic for Bose-Einstein condensation: Dayle G. Fried et al., Phys. Rev. Lett. 81 (1998) 3811

Spectroscopy and cooling of trapped antihydrogen

Some publications:

G. Gabrielse, in Fundamental Symmetries (Plenum, New York, 1987), p. 59

T. W. Hänsch and C. Zimmermann, Hyp. Int. 76 (1993) 47

J. T. M. Walraven, Hyp. Int. 76 (1993) 205

Claudio L. Cesar, Phys. Rev. A 64 (2001) 023418

K. Blaum and M. G. Raizen, White Paper to FLAIR at GSI, 2009

Saijun Wu, Roger C. Brown, William D. Phillips, and J. V. Porto, Phys. Rev. Lett. 106 (2011) 213001

P. H. Donnan, M. C. Fujiwara, and F. Robicheaux, J. Phys. B, 46 (2013) 025302

. . . and many others

Summary

. . . many things have been left out . . .

celebrated hydrogen success stories�

�1 S–2 S spectroscopy

�

�magnetic trapping

cold atomic beam apparatus pulsed Lyman-α laser cooling

ultra-stable 243 nm laser source Bose-Einstein condensation

optical frequency metrology

(future) antihydrogen spectroscopy

1 S–2 S: magnetic trapping (ALPHA, ATRAP)

hyperfine: polarized atomic beam (ASACUSA)

many, many orders of magnitude fewer atoms . . .

detection, however, can be much more efficient

→ hyperfine spectroscopy (ALPHA)