第 7 章 まとめ 110
7.2 将来の展望
7.2.2 本分光計で観測可能になる物理現象
本研究の結果，中赤外領域に現れる分子の基本振動バンドの回転構造全体を109 の分 解能で観測できるようになり，その遷移周波数を1011の精度で決定できるようになった．
これにより，今後観測できる可能性のある現象の例を挙げる．
■PH3 分子の反転スペクトル 図7.1はPH3 分子の反転運動によるエネルギー分裂を示 している．アンモニア（NH3）分子では，振動基底状態の反転スペクトルが数10 GHzの マイクロ波領域で観測されている．PH3 分子の反転スペクトルは，v2 = 1 状態で7 GHz 程度の分裂と予測されていたが[107]，最近の計算ではv2 = 3状態でも100 kHz程度と 予測されており，未だに観測されていない．ν2 振動モードの高振動励起状態ほど反転分 裂が大きいので，3ν2 バンド（2941 cm−1，88.16 THz）で観測できる可能性がある．
■CH3F分子の核スピン交換 CH3X分子には，水素原子核の全スピンが1/2と3/2の核 スピン異性体が存在し，この間の衝突緩和レートは非常に遅い．しかし，13CH3Fは核ス ピン状態の衝突緩和レートが速い. これは核スピン-核スピン相互作用で結びつく準位が偶 然近いエネルギーにあるためであるとされている[119]．CH3Fの準位構造を精密に決定 して，この予測を検証することができる．
分子構造を精密に決定できるようになって，振動回転相互作用や電気四重極モーメント などの分子理論の発展が促されれば，分子物理学や分子化学の発展に大きく貢献する．分 子に関して得られた知見は，天文学，医療分野への応用などへ波及していく．また，大き なスケールのエネルギー構造の中に隠れた小さな相互作用を観測できるようになり，振動 回転遷移に現れるパリティ対称性の破れや量子統計性の破れといった，分子に現れる量子 力学的効果についての新しい知見が得られる．さらに，高精度な遷移周波数測定は，電子
-図7.1 PH3分子の反転分裂．∆Einv(v2 = 3)はv3 = 3振動励起状態の反転エネル ギー分裂である．
陽子質量比など基礎物理定数の精密測定やその時間変化の観測にもつながる．
謝辞
本研究を行うにあたって，慶應義塾大学佐々田博之教授には，研究の方針，実験手法か ら理論的考察まで丁寧に指導していただき，心から感謝しております．特に，分子分光学 の歴史的な背景や本研究の立ち位置について，多くのことをご教授下さいました．本学位 論文の審査を引き受けて下さった東京理科大学盛永篤郎教授，慶應義塾大学中嶋敦教授，
岡朋治准教授，福嶋健二准教授には，論文を完成させるにあたって多くのご助言をいただ きました．慶應義塾大学長谷川太郎専任講師には，実験を行う上での貴重なご助言をいた だきました．ここに，篤くお礼申し上げます．
本研究で使用した光共振器吸収セルの製作にあたって，ネオアーク（株）石橋爾子博士 にご尽力いただきました．産業技術総合研究所洪鋒雷博士，稲場肇博士には，光周波数コ ムを使った周波数計測に関するご助言をいただきました．また，本研究で使用した光周波 数コムは，岩國加奈修士が産業技術総合研究所との共同研究で製作したものです．岩國氏 には，使用した光周波数コムの特性や基本的な使い方についても教えていただきました．
佐々田研究室でともに研究した修士課程中山裕天氏は，実験の手伝いや電子回路の製作作 業などしてくれました．その他研究室の皆様にも感謝申し上げます．
私が 2011年1月からドイツのマックスプランク量子光学研究所（MPQ: Max Planck Institute for Quantum Optics）に短期留学した際，光周波数コムのチームに受け入れてくれ たDr. Thomas UdemとDr. Ronald Holtzwarthに感謝いたします．MPQでデュアルコム 実験を教えてくれたDr. Nathalie Picqu´eと彼女のPh. D.課程の学生Mr. Takuro Ideguchi， Menlo Systemsでの光周波数コム研修において私をサポートしてくれたDr. Marc Fischer にも感謝申し上げます．
最後に，私が博士課程に進んで勉強を続けることを理解し，支援してくれた家族に感謝 を述べたいと思います．本当にありがとうございました．
2012年3月30日 大久保章
参考文献
[1] 朝永振一郎,量子力学(みすず書房, 1969), 2nd ed.
[2] G. W. F. Drake, ed., Springer Handbook of Atomic, Molecular, and Optical Physics (Springer, New York, 2006), 2nd ed.
[3] G. Herzberg, Molecular Spectra and Molecular Structure, vol. 2 : Infrared and Raman Spectra of Polyatomic Molecules (Van Nostrand, New York, 1951), 2nd ed.
[4] M. Abe, K. Takahata, and H. Sasada, “Sub-Doppler resolution 3.4-µm spectrometer with an efficient difference-frequency-generation source,” Opt. Lett. 34, 1744 (2009).
[5] J. L. Hall, C. J. Bord´e, and K. Uehara, “Direct optical resolution of the recoil effect using saturated absorption spectroscopy,” Phys. Rev. Lett. 37, 1339 (1976).
[6] W. Demtr¨oder, Laser Spectroscopy (Springer-Verlag, Berlin, 2008), 4th ed.
[7] R. L. M¨ossbauer, “Recoilless nuclear resonance absorption of gamma radiation,” Sci-ence 137, 731 (1962).
[8] C. Daussy, T. Marrel, A. Amy-Klein, C. T. Nguyen, C. J. Bord´e, and C. Chardonnet,
“Limit on the parity nonconserving energy difference between the enantiomers of a chiral molecule by laser spectroscopy,” Phys. Rev. Lett. 83, 1554 (1999).
[9] M. Quack, J. Stohner, and M. Willeke, “High-resolution spectroscopic studies and theory of parity violation in chiral molecules,” Annu. Rev. Phys. Chem. 59, 741 (2008).
[10] B. Darquie, C. Stoeffler, A. Shelkovnikov, C. Daussy, A. Amy-Klein, C. Chardonnet, S. Zrig, L. Guy, J. Crassous, P. Soulard, P. Asselin, T. R. Huet, P. Schwerdtfeger, R. Bast, and T. Saue, “Progress toward the first observation of parity violation in chiral molecules by high-resolution laser spectroscopy,” Chirality 22, 870 (2010).
[11] C. Daussy, M. Guinet, A. Amy-Klein, K. Djerroud, Y. Hermier, S. Briaudeau, C. J.
Bord´e, and C. Chardonnet, “Direct determination of the Boltzmann constant by an optical method,” Phys. Rev. Lett. 98, 250801 (2007).
[12] G. Casa, A. Castrillo, G. Galzerano, R. Wehr, A. Merlone, D. Di Serafino, P. La-porta, and L. Gianfrani, “Primary gas thermometry by means of laser-absorption spec-troscopy: Determination of the Boltzmann constant,” Phys. Rev. Lett. 100, 200801 (2008).
[13] P. Jensen and P. R. Bunker, Computational Molecular Spectroscopy (John-Wiley and Sons Inc., New York, 2000).
[14] G. Guelachvili and K. N. Rao, Handbook of Infrared Standards (Academic Press, Or-lando, 1986).
[15] G. Guelachvili and K. N. Rao, Handbook of Infrared Standards II (Academic Press, Orlando, 1993).
[16] T. J. Quinn, “Practical realization of the definition of the metre, including recom-mended radiations of other optical frequency standards (2001),” Metrologia 40, 103 (2003).
[17] F. Riehle, Frequency Standards: Basics and Applications (Wiley-VCH Verlag, Wein-heim, 2004).
[18] S. Svanberg, Atomic and Molecular Spectroscopy: Basic Aspects and Practical Appli-cations (Springer Verlag, Berlin, 2004), 4th ed.
[19] J. Tennyson, Astronomical Spectroscopy: An Introduction to the Atomic and Molecu-lar Physics of Astronomical Spectra (World Scientific Publishing Co. Inc., Singapore, 2010).
[20] T. T¨opfer, K. P. Petrov, Y. Mine, D. Jundt, R. F. Curl, and F. K. Tittel, “Room-temperature mid-infrared laser sensor for trace gas detection,” Appl. Opt. 36, 8042 (1997).
[21] K. Tsuji, H. Teshima, H. Sasada, and N. Yoshida, “An efficient and compact difference-frequency-generation spectrometer and its application to12CH3D/12CH4isotope ratio measurements,” Sensors 10, 6612 (2010).
[22] C. Wang and P. Sahay, “Breath analysis using laser spectroscopic techniques: Breath biomarkers, spectral fingerprints, and detection limits,” Sensors 9, 8230 (2009).
[23] T. Oka, “Spectroscopy and astronomy: H+3 from the laboratory to the galactic center,”
Faraday Discuss. 150, 9 (2011).
[24] N. Kolachevsky, A. Matveev, J. Alnis, C. Parthey, T. Steinmetz, T. Wilken, R. Holzwarth, T. Udem, and T. W. H¨ansch, “Testing the stability of the fine structure constant in the laboratory,” Space Sci. Rev. 148, 267 (2009).
[25] M. Fischer, N. Kolachevsky, M. Zimmermann, R. Holzwarth, T. Udem, and T. W.
H¨ansch, “New limits on the drift of fundamental constants from laboratory measure-ments,” Phys. Rev. Lett. 92, 230802 (2004).
[26] S. Schiller and V. Korobov, “Tests of time independence of the electron and nuclear masses with ultracold molecules,” Phys. Rev. A 71, 032505 (2005).
[27] P. Pyykk¨o, “Year-2008 nuclear quadrupole moments,” Mol. Phys. 106, 1965 (2008).
[28] J. L. Hall and J. A. Magyar, “High resolution saturated absorption studies of methane and some methyl-halides,” in “High-Resolution Laser Spectroscopy,” K. Shimoda, ed.
(Springer Verlag, Berlin, 1976).
[29] A. Amy-Klein, H. Vigu´e, and C. Chardonnet, “Absolute frequency measurement of
12CO2laser lines with a femtosecond laser comb and new determination of the12CO2
molecular constants and frequency grid,” J. Mol. Spectrosc. 228, 206 (2004).
[30] A. G. Maki, J. S. Wells, and M. D. Vanek, “Heterodyne frequency measurements on N2O near 930 cm−1,” J. Mol. Spectrosc. 138, 84 (1989).
[31] T. George, W. Urban, and A. L. Floch, “Improved mass-independent Dunham parame-ters for the ground state of CO and calibration frequencies for the fundamental band,”
J. Mol. Spectrosc. 165, 500 (1994).
[32] A. G. Maki and J. S. Wells, “New wavenumber calibration tables from heterodyne frequency measurements,” J. Res. NIST 97, 409 (1992).
[33] G. Magerl, J. M. Frey, W. A. Kreiner, and T. Oka, “Inverse Lamb dip spectroscopy using microwave modulation sidebands of CO2 laser lines,” Appl. Phys. Lett. 42, 656 (1983).
[34] B. Meyer, S. Saupe, M. H. Wappelhorst, T. George, F. Kuhnemann, M. Schneider, M. Havenith, and W. Urban, “CO laser side-band spectrometer: Sub-Doppler hetero-dyne frequency measurements around 5µm,” Appl. Phys. B 61, 169 (1995).
[35] J. T. Remillard, D. Uy, W. H. Weber, F. Capasso, C. Gmachl, A. L. Hutchinson, D. L.
Silvo, J. N. Ballargeon, and A. Y. Cho, “Sub-Doppler resolution limited Lamb-dip spectroscopy of NO with a quantum cascade distributed feedback laser,” Opt. Express 7, 243 (2000).
[36] E. V. Kovalchuk, D. Dekorsy, A. I. Lvovsky, C. Braxmaier, J. Mlynek, and A. Peters,
“High-resolution Doppler-free molecular spectroscopy with a continuous-wave optical parametric oscillator,” Opt. Lett. 26, 1430 (2001).
[37] O. Tadanaga, T. Yanagawa, Y. Nishida, H. Miyazawa, K. Magari, M. Asobe, and
H. Suzuki, “Efficient 3-µm difference frequency generation using direct-bonded quasi-phase-matched LiNbO3ridge waveguides,” Appl. Phys. Lett. 88, 061101 (2006).
[38] T. Oka, “Observation of the infrared spectrum of H+3,” Phys. Rev. Lett. 45, 531 (1980).
[39] T. R. Geballe and T. Oka, “Detection of H+3 in intersteller space,” Nature 384, 334 (1996).
[40] D. Mazzotti, P. D. Natale, G. Giusfredi, C. Fort, J. A. Mitchell, and L. Hollberg,
“Saturated-absorption spectroscopy with low-power difference-frequency radiation,”
Opt. Lett. 25, 350 (2000).
[41] P. Maddaloni, G. Gagliardi, P. Malara, and P. D. Natale, “A 3.5-mW continuous-wave difference-frequency source around 3 µm for sub-Doppler molecular spectroscopy,”
Appl. Phys. B: Lasers Opt. 80, 141 (2005).
[42] K. Anzai, X. Gao, H. Sasada, and N. Yoshida, “Narrow lamb dip of 3.4 µm band transition of methane with difference frequency generation and enhancement cavity,”
Jpn. J. Appl. Phys. 45, 2771 (2006).
[43] C. O. Weiss, G. Kramer, B. Lipphardt, and H. Schnatz, “Frequency Measurement and Control,” in “Optical Frequency Measurement by Conventional Frequency Multiplica-tion,” A. N. Luiten, ed. (Springer-Verlag, Berlin, 2000).
[44] J. L. Hall, “Nobel lecture: Defining and measuring optical frequencies,” Rev. Mod.
Phys. 78, 1279 (2006).
[45] T. W. H¨ansch, “Nobel lecture: Passion for precision,” Rev. Mod. Phys. 78, 1297 (2006).
[46] J. N. Eckstein, A. I. Ferguson, and T. W. H¨ansch, “High-resolution two-photon spec-troscopy with picosecond light pulses,” Phys. Rev. Lett. 40, 847 (1978).
[47] M. Kourogi, K. Nakagawa, and M. Ohtsu, “Wide-span optical frequency comb gen-erator for accurate optical frequency difference,” IEEE Quantum Electron. 29, 2693 (1993).
[48] M. Kourogi, T. Enami, and M. Ohtsu, “A monolithic optical frequency comb genera-tor,” IEEE Photon. Technol. Lett. 6, 214 (1994).
[49] M. Kourogi, T. Enami, and M. Ohtsu, “A coupled-cavity monolithic optical frequency comb generator ,” IEEE Photon. Technol. Lett. 8, 1698 (1996).
[50] Y. Awaji, K. Nakagawa, M. de Labachelerie, M. Ohtsu, and H. Sasada, “Optical fre-quency measurement of the H12C14N Lamb-dip-stabilized 1.5-µm diode laser,” Opt.
Lett. 20, 2024 (1995).
[51] K. Nakagawa, M. de Labachelerie, Y. Awaji, and M. Kourogi, “Accurate optical fre-quency atlas of the 1.5-µm bands of acetylene,” J. Opt. Soc. Am. B 13, 2708 (1996).
[52] C. Ishibashi, M. Kourogi, K. Imai, B. Widiyatmoko, A. Onae, and H. Sasada, “Abso-lute frequency measurement of the saturated absorption lines of methane in the 1.66-µm region,” Opt. Commun. 161, 223 (1999).
[53] T. Udem, J. Reichert, R. Holzwarth, and T. W. H¨ansch, “Accurate measurement of large optical frequency differences with a mode-locked laser,” Opt. Lett. 24, 881 (1999).
[54] S. A. Diddams, D. J. Jones, J. Ye, S. T. Cundiff, J. L. Hall, J. K. Ranka, R. S. Windeler, R. Holzwarth, T. Udem, and T. W. H¨ansch, “Direct link between microwave and op-tical frequencies with a 300 THz femtosecond laser comb,” Phys. Rev. Lett. 84, 5102 (2000).
[55] R. Holzwarth, T. Udem, T. W. H¨ansch, J. C. Knight, W. J. Wadsworth, and P. S. J.
Russell, “Optical frequency synthesizer for precision spectroscopy,” Phys. Rev. Lett.
85, 2264 (2000).
[56] D. J. Jones, S. A. Diddams, J. K. Ranka, A. Stentz, R. S. Windeler, J. L. Hall, and S. T. Cundiff, “Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis,” Science 288, 635 (2000).
[57] F.-L. Hong, K. Minoshima, A. Onae, H. Inaba, H. Takada, A. Hirai, H. Matsumoto, T. Sugiura, and M. Yoshida, “Broad-spectrum frequency comb generation and carrier-envelope offset frequency measurement by second-harmonic generation of a mode-locked fiber laser,” Opt. Lett. 28, 1516 (2003).
[58] F. Tauser, A. Leitenstorfer, and W. Zinth, “Amplified femtosecond pulses from an Er:fiber system: Nonlinear pulse shortening and selfreferencing detection of the carrier-envelope phase evolution,” Opt. Express 11, 594 (2011).
[59] P. Pal, W. H. Knox, I. Hartl, and M. E. Fermann, “Self referenced Yb-fiber-laser fre-quency comb using a dispersion micromanaged tapered holey fiber,” Opt. Express 15, 12161 (2007).
[60] C. G. Parthey, A. Matveev, J. Alnis, B. Bernhardt, A. Beyer, R. Holzwarth, A. Maistrou, R. Pohl, K. Predehl, T. Udem, T. Wilken, N. Kolachevsky, M. Abgrall, D. Rovera, C. Salomon, P. Laurent, and T. W. H¨ansch, “Improved measurement of the hydrogen1S–2S transition frequency,” Phys. Rev. Lett. 107, 203001 (2011).
[61] T. Udem, J. Reichert, R. Holzwarth, and T. W. H¨ansch, “Absolute optical frequency measurement of the cesium D1 line with a mode-locked laser,” Phys. Rev. Lett. 82,
3568 (1999).
[62] V. Gerginov, C. E. Tanner, S. Diddams, A. Bartels, and L. Hollberg, “Optical fre-quency measurements of6s2S1/2–6p2P3/2 transition in a133Cs atomic beam using a femtosecond laser frequency comb,” Phys. Rev. A 70, 042505 (2004).
[63] S. A. Diddams, T. Udem, J. C. Bergquist, E. A. Curtis, R. E. Drullinger, L. Hollberg, W. M. Itano, W. D. Lee, C. W. Oates, K. R. Vogel, and D. J. Wineland, “An optical clock based on a single trapped199Hg+ ion,” Science 293, 825 (2001).
[64] M. Takamoto, F.-L. Hong, R. Higashi, Y. Fujii, M. Imae, and H. Katori, “Improved fre-quency measurement of a one-dimensional optical lattice clock with a spin-polarized fermionic87Sr isotope,” J. Phys. Soc. Jpn. 75, 104302 (2006).
[65] D. Mazzotti, P. Cancio, A. Castrillo, I. Galli, G. Giusfredi, and P. D. Natale, “A comb-referenced difference-frequency spectrometer for cavity ring-down spectroscopy in the 4.5µm region,” J. Opt. A, Pure Appl. Opt. 8, S490 (2006).
[66] P. Malara, P. Maddaloni, G. Gagliardi, and P. D. Natale, “Absolute frequency measure-ment of molecular transitions by a direct link to a comb generated around 3-µm,” Opt.
Express 16, 8242 (2008).
[67] P. Maddaloni, P. Malara, E. D. Tommasi, M. D. Rosa, I. Ricciardi, G. Gagliardi, F. Tamassia, G. D. Lonardo, and P. D. Natale, “Absolute measurement of the S(0) and S(1) lines in the electric quadrupole fundamental band of D2 around 3 µm,” J.
Chem. Phys. 133, 154317 (2010).
[68] D. Mazzotti, P. Cancio, G. Giusfredi, P. D. Natale, and M. Prevedelli, “Frequency-comb-based absolute frequency measurements in the mid-infrared with a difference-frequency spectrometer,” Opt. Lett. 30, 997 (2005).
[69] K. Takahata, T. Kobayashi, H. Sasada, Y. Nakajima, H. Inaba, and F.-L. Hong,
“The absolute frequency measurement of sub-Doppler molecular lines using a 3.4-µm difference-frequency-generation spectrometer and a fiber-based frequency comb,”
Phys. Rev. A 80, 032518 (2009).
[70] G. Giusfredi, S. Bartalini, S. Borri, P. Cancio, I. Galli, D. Mazzotti, and P. D. Natale,
“Saturated-absorption cavity ring-down spectroscopy,” Phys. Rev. Lett. 104, 110801 (2010).
[71] K. Shimoda, “Line broadening and narrowing effects,” in “High-Resolution Laser Spectroscopy,” K. Shimoda, ed. (Springer-Verlag, Berlin, 1976).
[72] L. F´ejard, J. P. Champion, J. M. Jouvard, L. R. Brown, and A. S. Pine, “The intensities
of methane in the 3–5µm region revisited,” J. Mol. Phys. 201, 83 (2000).
[73] G. Buffa, A. D. Lieto, P. Minguzzi, O. Tarrini, and M. Tonelli, “Nuclear-quadrupole effects in the pressure broadening of molecular lines,” Phys. Rev. A 37, 3790 (1988).
[74] A. S. Pine, “Self-, N2, O2, H2, Ar, and He broadening in the ν3 band Q branch of CH4,” J. Chem. Phys. 97, 773 (1992).
[75] W. R. Bennett, Jr, “Hole burning effects in a He-Ne optical maser,” Phys. Rev. 126, 580 (1962).
[76] W. E. Lamb, Jr, “Theory of an optical maser,” Phys. Rev. 134, A1429 (1964).
[77] R. L. Barger and J. L. Hall, “Pressure shift and broadening of methane line at 3.39µ studied by laser-saturated molecular absorption,” Phys. Rev. Lett. 22, 4 (1969).
[78] A. Yariv and P. Yeh, Photonics: Optical Electronics in Modern Communications (Ox-ford University Press, New York, 2007), chap. 4, 6th ed.
[79] 菅滋正,櫛田孝司,分光測定(丸善, 1999).
[80] E. D. Black, “An introduction to Pound-Drever-Hall laser frequency stabilization,”
Am. J. Phys. 69, 79 (2011).
[81] R. V. Pound, “Electronic frequency stabilization of microwave oscillators,” Rev. Sci.
Instrum. 17, 490 (1946).
[82] R. W. P. Drever, J. L. Hall, F. V. Kowalski, J. Hough, G. M. Ford, A. J. Munley, and H. Ward, “Laser phase and frequency stabilization using an optical resonator,” Appl.
Phys. B 31, 97 (1983).
[83] T. Udem, R. Holtzwarth, and T. W. H¨ansch, “Optical frequency metrology,” Nature 416, 233 (2002).
[84] J. Ye, H. Schnatz, and L. W. Hollberg, “Optical frequency comb: From frequency metrology to optical phase control,” IEEE J. Sel. Top. Quantum Electron. 8, 1041 (1996).
[85] S. A. Diddams, “The evolving optical frequency comb,” J. Opt. Soc. Am. B 27, B51 (2010).
[86] N. Newbury, “Searching for applications with a fine-tooth comb,” Nature Photonics 5, 186 (2011).
[87] D. E. Spence, P. N. Kean, and W. Sibbett, “60-fsec pulse generation from a self-mode-locked Ti:sapphire laser,” Opt. Lett. 16, 42 (1991).
[88] F. Salin, J. Squier, and M. Pich´e, “Mode locking of Ti:AI2O3lasers and self-focusing:
a Gaussian approximation,” Opt. Lett. 16, 1674 (1991).
[89] M. Nakazawa, E. Yoshida, T. Sugawa, and Y. Kimura, “Continuum suppressed, uni-formly repetitive 136 fs pulse generation from an erbium-doped fibre laser with non-linear polarisation rotation,” Electronics Lett. 29, 1327 (1993).
[90] H. R. Telle, G. Steinmeyer, A. E. Dunlop, J. Stenger, D. H. Sutter, and U. Keller,
“Carrier-envelope offset phase control: A novel concept for absolute optical frequency measurement and ultrashort pulse generation,” Appl. Phys. B 69, 327 (1999).
[91] H. Inaba, Y. Daimon, F.-L. Hong, A. Onae, K. Minoshima, T. R. Schibli, H. Mat-sumoto, M. Hirano, T. Okuno, M. Onishi, and M. Nakazawa, “Long-term measure-ment of optical frequencies using a simple, robust and low-noise fiber based frequency comb,” Opt. Express 14, 5223 (2006).
[92] Y. Nakajima, H. Inaba, F.-L. Hong, A. Onae, K. Minoshima, T. Kobayashi, M. Nakazawa, and H. Matsumoto, “Optimized amplification of femtosecond optical pulses by dispersion management for octave-spanning optical frequency comb gener-ation,” Opt. Commun. 281, 4484 (2008).
[93] E. Jones and H. W. Thompson, “Vibration-rotation bands and molecular constants of methyl iodide,” Proc. R. Soc. Lond. A 288, 50 (1965).
[94] R. J. L. Popplewell and H. W. Thompson, “The vibrational-rotation bandν1of methyl iodide,” Spectrochim. Acta, Part A 25, 287 (1969).
[95] R. Paso, V.-M. Horneman, and R. Anttila, “Analysis of theν1 band of CH3I,” J. Mol.
Spectrosc. 101, 193 (1983).
[96] R. Paso, R. Anttila, and G. Guelachvili, “Perturbation in theν1band of CH3I,” J. Mol.
Spectrosc. 140, 46 (1990).
[97] Y. Morino and C. Hirose, “Microwave spectra of methyll iodide in the excited vibra-tional states. The Fermi resonance between theν5andν3+ν6states,” J. Mol. Spectrosc.
22, 99 (1967).
[98] D. Boucher, J. Burie, D. Dangoisse, J. Demaison, and A. Dubrulle, “Doppler-free rotational spectrum of methyl iodide. Nuclear-quadrupole, spin-rotation and nuclear shielding tensor of iodine,” Chem. Phys. 29, 323 (2011).
[99] A. Dubrulle, J. Burie, D. Boucher, F. Herlemont, and J. Demaison, “Microwave spectra of methyl chloride, methyl bromide, and methyl iodide in the v6 = 1 excited vibra-tional state,” J. Mol. Spectrosc. 88, 394 (1981).
[100] S. H. Young and S. G. Kukolich, “Microwave measurements and calculations of cou-pling effects in CH3I and CD3I,” J. Mol. Spectrosc. 114, 483 (1985).
[101] B. D. Osipov and M. N. Grabois, “Magnetic hyperfine structure and centrifugal distor-tion in quadrupole spectra of12CH3I and13CH3I,” J. Mol. Spectrosc. 111, 344 (1985).
[102] E. Arimondo, P. Glorieux, and T. Oka, “Radio-frequency spectroscopy inside a laser cavity; ”pure” nuclear quadrupole resonance of gaseous CH3I,” Phys. Rev. A 17, 1375 (1978).
[103] A. J. Gray and R. J. Butcher, “High-resolution laser-radiofrequency double resonance molecular spectroscopy,” Proc. Roy. Soc. Lond. A 445, 543 (1994).
[104] S. Carocci, A. D. Lieto, A. Menciassi, P. Minguzzi, and M. Tonelli, “High-resolution rotational spectroscopy of CH3I using a novel Doppler-free technique,” J. Mol. Spec-trosc. 175, 62 (1996).
[105] C. Ishibashi, R. Saneto, and H. Sasada, “Infrared radio-frequency double -resonance spectroscopy of molecular vibrational-overtone bands using a Fabry-Perot cavity-absorption cell,” J. Opt. Soc. Am. B 18, 1019 (2001).
[106] I. J. McNaught, “Structural parameters of methyl iodide by infrared spectroscopy,” J.
Chem. Educ. 59, 879 (1982).
[107] C. H. Townes and A. L. Schawlow, Microwave Spectroscopy (Dover, New York, 1975).
[108] S. Carocci, A. D. Lieto, A. D. Fanis, P. Minguzzi, and J. Pietila, “The molecular con-stants of12CH3I in the ground andv6 = 1excited vibrational state,” J. Mol. Spectrosc.
191, 368 (1998).
[109] K. Uehara, K. Sakurai, and K. Shimoda, “Stark effect of the absorption line of methane observed by the 3.391µm He-Ne maser,” J. Phys. Soc. Jpn. 26, 1018 (1969).
[110] R. F. Curl, Jr., “Infrared-radio frequency double resonance observations of pure rota-tionalQ-branch transitions of methane,” J. Mol. Spectrosc. 48, 165 (1973).
[111] R. F. Curl, T. Oka, and D. S. Smith, “The observation of a pure rotationalQ-branch transition of methane by infrared-radio frequency double resonance,” J. Mol. Spec-trosc. 46, 518 (1973).
[112] E. Baumann, F. R. Giorgetta, W. C. Swann, A. M. Zolot, I. Coddington, and N. R.
Newbury, “Spectroscopy of the methaneν3band with an accurate midinfrared coherent dual-comb spectrometer,” Phys. Rev. A 84, 062513 (2011).
[113] 小尾欣一,分光測定の基礎(講談社, 2009).
[114] L. S. Rothman, I. E. Gordon, A. Barbe, D. C. Benner, P. E. Bernath, M. Birk, V. Boudon, L. R. Brown, A. Campargue, J. P. Champion, K. Chance, L. H. Coudert, V. Dana, V. M. Devi, S. Fally, J.-M. Flaud, R. Gamache, A. Goldman, D. Jacquemart,
I. Kleiner, N. Lacome, W. J. Lafferty, J.-Y. Mandin, S. T. Massie, S. N. Mikhailenko, C. E. Miller, N. Moazzen-Ahmadi, O. V. Naumenko, A. V. Nikitin, J. Orphal, V. I.
Perevalov, A. Perrin, A. Predoi-Cross, C. P. Rinsland, M. Rotger, M. Simeckova, M. A. H. Smith, K. Sung, S. A. Tashukun, J. Tennyson, R. A. Toth, A. C. Vandaele, and J. V. Auwera, “The HITRAN 2008 molecular spectroscopic database,” J. Quant.
Spectrosc. Radiat. Transfer 110, 533 (2009).
[115] P. S. Ering, D. A. Tyurikov, G. Kramer, and B. Lipphardt, “Measurement of the abso-lute frequency of the methane E-line at 88 THz,” Opt. Commun. 151, 229 (1998).
[116] J. L. Hall and C. J. Bord´e, “Shift and broadening of saturated absorption resonances due to curvature of the laser wave front,” Appl. Phys. Lett. 29, 788 (1976).
[117] M. Takami, K. Uehara, and K. Shimoda, “Rotational transitions of CH4in thev3 = 1 excited state observed by an infrared-microwave double resonance method,” Jpn. J.
Appl. Phys. 12, 924 (1973).
[118] C. J. Pursell and D. P. Weliky, “Pure rotational transitions in theν3 state of methane,”
J. Mol. Spectrosc. 153, 303 (1992).
[119] P. L. Chapovsky and L. J. F. Hermans, “Nuclear spin conversion in polyatomic molecules,” Annu. Rev. Phys. Chem. 50, 315 (1999).
付録 A
差周波発生法
A.1 2 次の非線形光学効果
光によって媒質中に誘起される分極P は，印加電場Eのべき関数として
Pi =ε0
∑
j
χ(1)ij Ej+∑
j,k
χ(2)ijkEjEk+· · ·
(A.1)
と表される．ここで，i, j, kは空間座標x, y, zの和を取るための添え字である．χ(1)ij は線 形感受率で2階のテンソル，χ(2)ijk は2次の非線形感受率で3階のテンソルである．媒質 に入射する光電場振幅|E|が小さい場合には第 1項の線形分極が支配的であるが，レー ザー光や光パルスなど高強度の光が入射した場合には非線形分極が無視できなくなる．
(A.1) 式の第2項を2次の分極Pi(2) と表記する．ここでは2次の非線形光学効果につ
いて議論し，3次以上の非線形感受率は無視する．また，これ以降は簡単のためにスカ ラー量での議論とする．これは，等方性媒質中の直線偏光の伝搬に対応する．
2次の非線形媒質にω1，ω2 と角周波数の異なる2つの光が入射する場合を考える．入 射電場を
E(t) = 1 2
[E1eiω1t+E2eiω2t]
+ c.c. (A.2)
と表すと，これによって誘起される2次の非線形分極は
P(2)(t) = ε0χ(2) 4
[E1E1∗ +E2E2∗+E12ei2ω1t+E22ei2ω2t
+ 2E1E2ei(ω1+ω2)t+ 2E1E2∗ei(ω1−ω2)t]
+ c.c. (A.3)
となる．ここで，E1，E2 は角周波数ω1，ω2 の入射複素電場である．したがって，2次 の非線形分極によって角周波数が0，2ω1，2ω2，ω1+ω2，ω1−ω2 の5つの光が発生し うる．